Patent Abstract:
A system for separating contaminants from an air stream entering a sealed case through a vent fitting communicating to the interior cavity of the case includes a contaminant separator having a housing enclosing a chamber, an inlet and outlet communicating with the chamber, a baffle located in the chamber and producing a constricted fluid flow passageway between the inlet and the outlet.

Full Description:
BACKGROUND OF THE INVENTION 
   The preferred embodiment relates generally to a case that contains the components of a power transmission for a motor vehicle, and particularly to an vent apparatus for allowing air to enter and leave the case while preventing ingress of water and contaminants to the case. 
   A sealed transmission case requires a vent due to changes that occur in the temperature of the air held in the transmission case. The equation of state or characteristic equation of a perfect gas, derived from Boyle&#39;s law and either of Charles&#39; laws for an ideal gas, states p*V=w*R*T, wherein p is gas pressure, V is gas volume, w is weight of the gas, R is the gas constant, and T is gas temperature. If the volume of air in the transmission case is constant due to the case being sealed, then changes in the temperature of air in the transmission case would cause pressure within the case to increase and decrease. If the transmission case were not vented and the temperature of air in the sealed volume of the case were increased, air pressure within the case would increase. That increase in air pressure in the case could cause transmission fluid to be forced from the case through the fill tube provided to add transmission fluid to the case. A decrease in air pressure could cause water or contaminants to enter the case past external transmission seals. Therefore, a transmission case is vented to maintain a zero pressure differential between its interior and the ambient, atmospheric air pressure. 
   However, venting the transmission case to allow air to enter the case through a vent while preventing water and contaminants from being drawn into the transmission case presents challenging technical issues. There is a need to provide a simple, inexpensive, yet reliable technique for admitting air through a vent and excluding water and other contaminants from entering the transmission case through the vent. 
   SUMMARY OF THE INVENTION 
   A system for separating contaminants from an airstreams entering a sealed case through a vent fitting communicating to the interior cavity of the case includes a contaminant separator having a housing enclosing a chamber, an inlet and outlet communicating with the chamber, a baffle located in the chamber and producing a constricted fluid flow passageway between the inlet and the outlet. A bottom surface within the chamber supports material separated from an airstreams that passes between the inlet and the outlet. The separated contaminants can exit the housing through a drain in the bottom surface. 
   The contaminant separator is formed of molded plastic to prevent corrosion and is readily stored at a high elevation in the engine compartment of a motor vehicle a short distance from the transmission case so that a hose connecting them is also short. The contaminant separator housing includes a baffle which prevents entry of water and solid contaminants in to the case. 
   The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 

   
     DESCRIPTION OF THE DRAWINGS 
     These and other advantages will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
       FIG. 1  is an isometric view of a contaminant separator for separating entrained contaminants from air entering a transmission case; 
       FIG. 2  is front view of the contaminant separator illustrated in  FIG. 1 ; 
       FIG. 3  is a side view of the contaminant separator illustrated in  FIG. 1 ; and 
       FIG. 4  is front view of an alternate embodiment of a contaminant separator containing multiple baffles. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1-3  show a system  10  including a contaminant separator  12  for separating liquid, such as water, and solid contaminants from air entering a transmission case. The contaminant separator  12  includes a thin walled housing  13  preferably formed of molded plastic. The housing  13  is in the form of a hollow, six-faced container, all of whose faces are rectangles lying in pairs of parallel planes, such as a cube, the length of each edge being about two inches. However, the housing may be spherical or another suitable shape. The top  14  supports an inlet  16 , such as a fitting, which extends about 0.25 inches above the plane of the top, the inlet  16  having an opening  18  communicating with the interior of the contaminant separator  12  and through which atmospheric air enters and leaves the contaminant separator. The top  14  also supports a outlet  20 , such as nozzle, which extends about 0.25 inches above the plane of the top, the outlet  20  having an opening  22  communicating with the interior of the of the contaminant separator  12  and through which air leaves the separator and enters the transmission case  24  through a vent fitting  26  located on the case  24 . Outlet nozzle  20  is formed to receive and retain thereon the end of a flexible hose  28 , whose opposite end  30  is secured to the vent fitting  26  on the transmission case  24 . 
   In one embodiment the interior of the contaminant separator  12  is a single chamber divided by a baffle  32  located between the intake air fitting  16  and the transmission case supply nozzle  20 . The baffle  32  is supported on and secured to the inner surfaces of the top  14 , front side  34  and rear side  36 . The baffle  32  has a free edge  38 , which is spaced about 0.125 inches above the inner surface of the bottom  40 . 
   Ambient air entering the contaminant separator  12  through fitting  16  flows downward and along the baffle  32 , past its free edge  38 , and then upward to and through the transmission case air supply nozzle  20 . This circuitous route around the baffle  32  causes water droplets and other contaminants to strike the baffle  32  and to fall onto the inner surface of the bottom  40 , thereby preventing the contaminants from being carried along in the stream of incoming air to the transmission case supply nozzle  20 . As a result, most of the water and entrained contaminants entering the contaminant separator  12  through the air intake fitting  16  drop to the bottom surface  40  and can be removed from the contaminant separator  12  through a drain fitting  42  located there. 
   A channel  44  encircling the contaminant separator housing  13  and located approximately mid-way between the top  14  and bottom  40  provides a recess in which a band or zip-tie  46  engages the housing  12  and is secured preferably in the engine compartment of the vehicle, in which the transmission case  24  is installed. In this way, the contaminant separator housing  13  can be secured against movement in the vehicle. 
     FIG. 4  illustrated a second embodiment, in which an alternate contaminant separator  50  includes three baffles  52 ,  53 ,  54  between the inlet  18  and outlet  20 . The baffles  52 ,  53 ,  54  may be planar and substantially normal to the top  14 , planar and inclined respect to the top, or arcuate, as shown. The intermediate baffle  53  includes a free edge  55  that is spaced about 0.125 inches from the inner surface of the top  14 . The left side outer baffle  52  includes a free edge  56  that is spaced about 0.125 inches from the inner surface of the bottom  40 . The right side outer baffle  54  includes a free edge  58  that is spaced about 0.125 inches from the inner surface of the bottom  40 . 
   Ambient air entering the contaminant separator  50  through fitting  16  flows downward and along the baffle  52 , across its free edge  38 , upward between baffles  52  and  53 , across the free edge  55  of baffle  53 , downward between baffles  53  and  54 , across the free edge  58  of baffle  54 , and upward to and through the transmission case air supply nozzle  20 . Most of the water and entrained contaminants entering the contaminant separator  50  through the air intake fitting  16  drop to the bottom surface  40  and can be removed from the contaminant separator  12  through a drain fitting  42 . 
   Alternatively, the contaminant separator housing  13  may be secured to the vehicle using a member  48  with flexible, tapered, circular serrations  50  on its outer surface, commonly called a Christmas tree, located on the side  36  of the contaminant separator housing  13 . A receptacle  60 , of the type commonly used in the automotive industry, which is secured to the vehicle, includes flexible, tapered, circular serrations  62 , which resiliently engage the serrations  50  of the Christmas tree connector member  48 , thereby securing housing  13  in its correct location in the vehicle. 
   Although the preferred embodiments have been described with reference to a transmission case  24 , such as a case containing the mechanical, hydraulic, and electronic components of an automatic transmission or manual transmission, the case  24  may contain other components, such as those for a power transfer device, such as a transfer case, which selective transmits rotating power from a transmission output shaft to a secondary drive shaft and a secondary set of vehicle wheels when four-wheel drive operation is desired. 
   In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.

Technology Classification (CPC): 1