Abstract:
A method and apparatus for attaching a transmission filter to a pump is provided. The filter and pump include complimentary engagement features such that the filter is inserted into the pump and thereafter rotated approximately 90 degrees to engage a twistlock feature. In this manner, filter attachment is maintained without additional fasteners, spring clips, clamping plates, etc., thereby reducing material cost.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/589,282, filed Jul. 20, 2004, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     According to a preferred embodiment of the present invention, a method and apparatus is provided for conveniently attaching a transmission filter to a pump.  
       BACKGROUND OF THE INVENTION  
       [0003]     Transmission filters and pumps are generally manufactured as individual components and thereafter assembled together as part of a vehicle transmission. Typically such assembly requires fasteners, is labor intensive and is unnecessarily prone to failure. More precisely, implementation of fasteners to assemble the filter to the pump incurs the additional cost associated with the fasteners, requires precision to properly engage the fasteners, and can lead to an inadequate connection between the filter and pump if the fasteners are improperly engaged and/or prematurely fail. Finally, fasteners that are improperly engaged and/or prematurely fail can come loose and result in an objectionable noise while the vehicle is operated.  
       SUMMARY OF THE INVENTION  
       [0004]     It is an object of the present invention to provide an improved method and apparatus for attaching a transmission filter to a pump.  
         [0005]     A filter assembly according to a preferred embodiment of the present invention includes a twistlock attachment feature. More precisely, the filter is inserted into the pump and thereafter rotated approximately 90 degrees to engage the twistlock feature. In this manner, filter attachment is maintained without additional fasteners, spring clips, clamping plates, etc., thereby reducing material cost. Elimination of these parts also error proofs the assembled components in that the fasteners, spring clips, clamping plates, etc. cannot inadvertently be dropped into the transmission causing other parts to fail and/or giving rise to an objectionable noise.  
         [0006]     In a preferred embodiment, the filter includes a filter nozzle composed of injection molded plastic and integrally extending from a plastic filter housing. In this manner, multiple components can be simultaneously produced from a single mold thereby saving cost associated with manufacturing and assembly.  
         [0007]     The above features and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic diagram of a portion of a hydraulic system incorporating the present invention;  
         [0009]      FIG. 2  is an isometric view of a filter assembly incorporating the present invention;  
         [0010]      FIG. 3  is an isometric view of a pump assembly incorporating the present invention; and  
         [0011]      FIG. 4  is a sectional view of a portion of the filter assembly shown in  FIG. 2  attached to the pump assembly shown in  FIG. 3 .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     Referring to the drawings wherein like characters represent the same or corresponding parts through the several views, there is seen in  FIG. 1 a  schematic representation of a transmission fluid distribution system  8  which includes a sump or reservoir  10  preferably containing hydraulic fluid. A transmission pump  12  draws the hydraulic fluid from the reservoir  10  through a filter  14 . The pump  12  delivers pressurized hydraulic fluid to a transmission  16 . The maximum pressure at the pump outlet is determined by a pressure regulator valve  18 , which delivers excess pump flow to the filter  14 . According to a preferred embodiment of the present invention, the hydraulic fluid first satisfies the transmission pressure requirements, then satisfies the torque converter pressure requirements, then supplies some lube and cooling, and thereafter the excess fluid is returned to the filter  14 .  
         [0013]     Referring to  FIG. 2 , the filter assembly  14  includes a housing  24  which has a filter element (not shown) secured therein. A generally cylindrical filter outlet portion  28  extends substantially perpendicular from the housing  24 , and according to a preferred embodiment the outlet portion  28  terminates in a filter nozzle  30 . At least a portion of the housing  24 , the filter outlet portion  28  and the nozzle  30  are preferably a single injection molded component. This embodiment is particularly advantageous in that the filter assembly  14  incorporates an annular nozzle design without additional parts such as a conical insert to create the nozzle function.  
         [0014]     The filter outlet portion  28  preferably includes an engagement flange  32 . The engagement flange  32  extends in a radially outward direction from the filter outlet portion  28  and is disposed about the circumference thereof. According to a preferred embodiment, the engagement flange  32  defines opposed recessed portions  34 . The engagement flange  32  in conjunction with a complimentary shoulder  70  (shown in  FIG. 3  and described in detail hereinafter) form a twistlock feature adapted to maintain engagement of the filter  14  and pump  12  without additional fasteners.  
         [0015]     Referring to  FIG. 3 , the pump  12  includes a housing  40  configured to define a generally cylindrical inlet bore  48 . The inlet bore  48  is adapted to receive the filter outlet portion  28  (shown in  FIG. 2 ). The diameter of the inlet bore  48  is reduced by the shoulder  70  adapted to accommodate the engagement flange  32  and thereby maintain engagement of the filter assembly  14  (shown in  FIG. 2 ) and the pump  12 . As best shown in  FIG. 4 , the shoulder  70  includes a downstream portion  72  and an upstream portion  74  which define a slot  76  therebetween. Referring again to  FIG. 3 , the shoulder  70  further includes opposed notched portions  78 .  
         [0016]     To assemble the filter  14  to the pump  12 , the filter outlet portion  28  is inserted into the pump inlet bore  48  such that the engagement flange  32  is aligned with the notched portions  78  of the shoulder  70 . Thereafter, the filter  14  is rotated approximately 90 degrees relative to the pump  12  such that the engagement flange  32  is retained in the pump slot  76 . Therefore, the engagement flange  32  of the filter  14  and the shoulder  70  of the pump  12  cooperate to form a twistlock feature whereby the filter  14  is assembled to the pump  12  without any additional fasteners.  FIG. 4  shows the filter  14  assembled to the pump  12  such that the engagement flange  32  is disposed within the slot  76 , and the engagement flange  32  is locked into position by downstream portion  72  and upstream portion  74  of the shoulder  70 .  
         [0017]     In a preferred embodiment, the present invention may be implemented with the nozzle feature disclosed in U.S. Provisional Application No. 60/589,275 entitled “Improved Transmission Pump and Filter,” filed Jul. 20, 2004, which is hereby incorporated by reference in its entirety. Advantageously, manufacturing tolerance of the engagement flange  32  and the pump slot  76  are capable of maintaining a nozzle passage  64  (shown in  FIG. 2  of the incorporated Application) width of 1.5±0.5 mm. It has been established that such a nozzle passage width effectively minimizes cavitation, as described in the incorporated application, within the entire range of variation, thereby yielding robust performance from the nozzle in conjunction with the ease of assembly of the present invention. It has further been established that the injection molded embodiment provides an interface between the engagement flange  32  and the shoulder  70  is sufficiently strong to resist the back pressure of the nozzle (described in detail in the incorporated application). This embodiment is particularly advantageous because metal plates and corresponding fasteners are not required for implementation, thereby reducing cost associated with additional components and assembly.  
         [0018]     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.