Filter unit

Abstract

A filter unit includes a body portion having a proximal end and a distal end. An engagement protrusion extends from the proximal end. The engagement protrusion includes a first portion that has a first radius of curvature and a second portion opposing the first portion that has a second radius of curvature that is larger than the first radius of curvature. A protruding retention surface is disposed on and extends radially outward from the body portion. The protruding retention surface is adapted to secure the filter unit in a filter head assembly.

The invention claimed is: 
     
         1 . A filter unit comprising:
 a body portion having a proximal end and a distal end;   an engagement protrusion extending from the proximal end, the engagement protrusion having a first portion that includes a first radius of curvature and a second portion opposing the first portion that includes a second radius of curvature that is larger than the first radius of curvature; and   a protruding retention surface disposed on and extending radially outward from the body portion, the protruding retention surface adapted to secure the filter unit in a filter head assembly.   
     
     
         2 . The filter unit of  claim 1 , further comprising:
 a first recessed retention surface disposed on the body portion, the first recessed retention surface adapted to secure the filter unit in the filter head assembly.   
     
     
         3 . The filter unit of  claim 2 , further comprising:
 a second recessed retention surface disposed on the body portion, the second recessed retention surface adapted to secure the filter unit in the filter head assembly.   
     
     
         4 . The filter unit of  claim 3 , wherein the first recessed retention surface and the second recessed retention surface are on substantially opposing sides of the body portion. 
     
     
         5 . The filter unit of  claim 1 , further comprising:
 a central axis extending substantially centrally through the longitudinal extent of the filter unit, wherein a first plane is defined between the central axis and the first portion of the engagement protrusion and a second plane is defined between the central axis and the protruding retention surface, and wherein the angle between the first plane and the second plane is approximately 10 degrees.   
     
     
         6 . The filter unit of  claim 1 , further comprising:
 a central axis extending substantially centrally through the longitudinal extent of the filter unit, wherein a first plane is defined between the central axis and the first portion of the engagement protrusion and a second plane is defined between the central axis and the first recessed retention surface, and wherein the angle between the first plane and the second plane is approximately 26 degrees.   
     
     
         7 . The filter unit of  claim 1 , wherein the distance from a top edge of the engagement protrusion to the protruding retention surface is approximately 41.2 millimeters. 
     
     
         8 . The filter unit of  claim 2 , wherein the distance from a top edge of the engagement protrusion to the first recessed retention surface is approximately 62.8 millimeters. 
     
     
         9 . A filter unit comprising:
 a substantially cylindrical body portion having a proximal end and a distal end;   an engagement protrusion extending from the proximal end of the cylindrical body portion;   first and second distinct retention surfaces disposed in the cylindrical body portion; and   a third distinct retention surface disposed on and extending radially outward from the cylindrical body portion.   
     
     
         10 . The filter unit of  claim 9 , wherein the first and second distinct retention surfaces are defined by first and second grooves disposed in the cylindrical body portion. 
     
     
         11 . The filter unit of  claim 9 , wherein the distance from a top edge of the engagement protrusion to the third retention surface is approximately 41.2 millimeters. 
     
     
         12 . The filter unit of  claim 11 , wherein the distance from a top edge of the engagement protrusion to the first retention surface is approximately 62.8 millimeters. 
     
     
         13 . The filter unit of  claim 10 , further comprising:
 a central axis extending substantially centrally through the longitudinal extent of the filter unit; and   an outlet disposed on the engagement protrusion, wherein the central axis extends through the outlet.   
     
     
         14 . The filter unit of  claim 9 , wherein the first and second distinct retention surfaces are disposed on substantially opposing sides of the cylindrical body portion. 
     
     
         15 . A filter unit comprising:
 a body portion including an exterior wall and having a proximal end and a distal end;   an engagement protrusion extending from the proximal end, the engagement protrusion having a cross-section with only one axis of symmetry; and   a retention surface disposed on the body portion, the retention surface defined by one of:
 a radially extending member that protrudes outwardly from the body portion; and 
 a groove defined in the exterior wall of the body portion. 
   
     
     
         16 . The filter unit of  claim 15 , further comprising:
 a central axis extending substantially centrally through the longitudinal extent of the filter unit, wherein a first plane is defined between the central axis and the first portion of the engagement protrusion and a second plane is defined between the central axis and the retention surface, and wherein the angle between the first plane and the second plane is approximately 10 degrees.   
     
     
         17 . The filter unit of  claim 15 , further comprising:
 a central axis extending substantially centrally through the longitudinal extent of the filter unit, wherein a first plane is defined between the central axis and the first portion of the engagement protrusion and a second plane is defined between the central axis and the retention surface, and wherein the angle between the first plane and the second plane is approximately 26 degrees.   
     
     
         18 . The filter unit of  claim 15 , wherein the distance from a top edge of the engagement protrusion to a first gasket is approximately 2.7 millimeters. 
     
     
         19 . The filter unit of  claim 18 , wherein the distance from the top edge of the engagement protrusion to a second gasket is approximately 18.7 millimeters. 
     
     
         20 . The filter unit of  claim 18 , wherein the distance from the top edge of the engagement protrusion to the retention surface is approximately 41.2 millimeters.