Patent Publication Number: US-8973282-B2

Title: Secondary lint trap for residential laundry dryer

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/467,059 filed on 24 Aug. 2006 and entitled SECONDARY LINT TRAP FOR RESIDENTIAL LAUNDRY DRYER, the content of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure concerns a secondary lint trap for use with laundry dryers in residential building suites. 
     BACKGROUND 
     Modern multiple-suite high-rise residential buildings have ventilation systems with floor or ceiling-embedded vent ducts. Each suite has one or more vent ducts. Exhaust conduits are used to connect exhaust air sources within the suite to one of the vent ducts. Bathroom fans, range hood fans and laundry dryers are typical exhaust air sources. For example, one exhaust conduit may be connected between the exhaust outlet of a bathroom fan and a vent duct, a second exhaust conduit may be connected between the exhaust outlet of a range hood fan and a vent duct, a third conduit may be connected between the exhaust outlet of a laundry dryer and a vent duct, etc. Exhaust air is expelled into the conduits and exhausted from the building through the vent ducts. 
     Conventional residential laundry dryers have built-in primary lint traps. However, a dryer&#39;s damp, warm exhaust air may contain a substantial amount of excess lint which is not trapped by the dryer&#39;s primary lint trap. A secondary lint trap can be coupled between the dryer&#39;s exhaust outlet and the building&#39;s vent duct to reduce the accumulation of lint in the vent duct. 
     A stackable laundry washer/dryer unit  10  ( FIG. 1 ) incorporating a dryer  12  stacked atop a washer  14  is often used to conserve space in a high-rise building suite.  FIG. 1  depicts two alternative prior art configurations for coupling dryer  12  to one or the other of prior art secondary lint traps  16 A,  16 B. As shown to the right in  FIG. 1 , dryer  12 &#39;s exhaust outlet  18  can be coupled through conduit  20 A, 90° elbow  22 A and conduit  24 A to the inlet  26 A of prior art secondary lint trap  16 A. Secondary lint trap  16 A&#39;s outlet  28 A is coupled through conduit  30 A and 90° elbow  32 A to ceiling-embedded vent duct  34 A. Alternatively, as shown to the left in  FIG. 1 , dryer  12 &#39;s exhaust outlet  18  can be coupled through conduit  20 B, 90° elbow  22 B, conduit  21 B, 90° elbow  23 B and conduit  24 B to the inlet  26 B of prior art secondary lint trap  16 B. Secondary lint trap  16 B&#39;s outlet  28 B is coupled through conduit  30 B and 90° elbow  32 B to ceiling-embedded vent duct  34 B. 
     It is generally recommended that no more than two 90° elbows and no more than 15 feet of conduit be used to connect a laundry dryer&#39;s exhaust outlet to a building-embedded vent duct. Otherwise, air pressure in the exhaust conduit(s) and vent duct is reduced, resulting in inefficient operation of the dryer and potentially necessitating installation of an inline fan (not shown) to increase air pressure in the exhaust conduit(s) and vent duct. The prior art configuration shown to the right in  FIG. 1  is somewhat preferable to the configuration on the left, because the configuration on the right has only two 90° elbows  22 A,  32 A whereas the configuration on the left has three 90° elbows  22 B,  23 B,  32 B. The configuration on the right is also preferable if the combined length of conduits  20 A,  24 A and  30 A is less than the combined length of conduits  20 B,  21 B,  24 B and  30 B; particularly if the combined length of conduits  20 B,  21 B,  24 B and  30 B exceeds 15 feet. 
     It is not always possible to adopt a 2-elbow configuration like that shown to the right in  FIG. 1 , nor is it always possible to adopt a configuration requiring no more than 15 feet of conduit to connect a dryer&#39;s exhaust outlet to a suite&#39;s built-in vent duct. This is problematic because if moisture-laden air is not efficiently exhausted, moisture may accumulate inside the elbows, exhaust conduit(s), vent duct, etc. potentially causing water damage. Moreover, if a prior art secondary lint trap is mounted in a location which is difficult to reach, the suite&#39;s occupant(s) may be unable or may be disinclined to remove accumulated lint from the secondary lint trap with sufficient frequency. Lint may accordingly accumulate in the secondary lint trap to a point which further reduces the dryer&#39;s efficiency. In an extreme case, accumulated lint can pose a fire hazard. 
     The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Exemplary embodiments are illustrated in referenced figures of the drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
         FIG. 1  is an isometric illustration depicting two alternative prior art configurations for connecting a laundry dryer through a prior art secondary lint trap to a building-embedded vent duct. 
         FIG. 2  is an isometric illustration depicting connection of a laundry dryer to a building-embedded vent duct through an improved secondary lint trap. 
         FIG. 3  is an enlarged isometric illustration of the  FIG. 2  secondary lint trap. 
         FIG. 4  is an exploded isometric illustration of the  FIG. 3  secondary lint trap. 
     
    
    
     DESCRIPTION 
     Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense. 
       FIG. 2  depicts a stackable laundry washer/dryer unit  10  incorporating dryer  12  and washer  14  as described above in relation to  FIG. 1 . Dryer  12 &#39;s exhaust outlet  18  is coupled through 90° elbow  40  and conduit  42  to the inlet collar  44  of secondary lint trap  46 . Secondary lint trap  46 &#39;s outlet collar  48  is coupled through conduit  50  and 90° elbow  52  to ceiling-embedded vent duct  54 . 
     As best seen in  FIGS. 3 and 4 , secondary lint trap  46  includes an elongate housing  56  which slidably receives a flat, elongate removable tray  58  through frontal opening  60 . Housing  56  may be formed by fastening the side and rear edges  62 ,  64 ,  66  of a channel-shaped, sheet metal top part  68  to the corresponding side and rear edges  72 ,  74 ,  76  of a flat, sheet metal bottom part  78 . Top part  68  can be fastened to bottom part  78  by button-locking top part  68 &#39;s side and rear edges  62 ,  64 ,  66  to bottom part  78 &#39;s side and rear edges  72 ,  74 ,  76  respectively. 
     Inlet collar  44 &#39;s flanged rim  80  is circumferentially fastened around bottom part  78 &#39;s downward-facing inlet aperture  82  so that collar  44  protrudes downwardly from the bottom side of housing  56 &#39;s bottom part  78 . Inlet collar  44  and rim  80  are formed of sheet metal. Rim  80  may be welded around inlet aperture  82 . 
     Outlet collar  48 &#39;s flanged rim  84  is circumferentially fastened around top part  68 &#39;s upward-facing outlet aperture  86  so that collar  48  protrudes upwardly from the top side of housing  56 &#39;s top part  68 . Outlet collar  48  and its rim  84  are formed of sheet metal. Rim  84  may be welded around outlet aperture  86 . 
     Housing  56  is mounted atop dryer  12  such that inlet and outlet collars  44 ,  48  extend rearwardly of dryer  12 &#39;s rear wall  88 . Such rearward extension facilitates coupling of dryer  12 &#39;s exhaust outlet  18  (which protrudes horizontally and rearwardly from dryer  12 &#39;s rear wall  88 ) to inlet collar  44  through one 90° elbow  40  having an upward-facing outlet aligned with inlet collar  44  via one short, substantially straight, elbowless conduit  42 . Such rearward extension also facilitates coupling of vent duct  54  to outlet collar  48  through one 90° elbow  52  having a downward-facing outlet aligned with outlet collar  48  via another short, substantially straight, elbowless conduit  50 . Double-sided foam tape can be used to mount housing  56  atop dryer  12 . 
     Tray  58  is sized and shaped for snug-fit, slidably removable insertion through housing  56 &#39;s frontal opening  60 . An aperture  92  is formed near the rearward end  94  of tray  58 . Aperture  92  is aligned between apertures  82 ,  86  which are aligned with one another when top and bottom parts  68 ,  78  are assembled to form housing  56 . Aperture  92  is thus aligned between inlet and outlet collars  44 ,  48  when tray  58  is fully inserted within housing  56 . A stainless steel mesh screen  96  is mounted in aperture  92  by fastening apertured frame  98  over screen  96  and to the underside of tray  58 , such that frame  98  circumferentially surrounds aperture  92 . A handle  100  is provided on the forward end  102  of tray  58 . The length of housing  56  and tray  58  (i.e. the displacement between housing  56 &#39;s rear edges  66 ,  76  and the forward end  102  of tray  58 ) is sufficient to allow handle  100  to protrude slightly forwardly of dryer  12 &#39;s front wall  104  when tray  58  is fully inserted within housing  56 . This allows handle  100  to be easily grasped for removal of tray  58  from housing  56  as explained below. 
     During operation of dryer  12 , lint-laden exhaust air is expelled horizontally and rearwardly through dryer  12 &#39;s exhaust outlet  18  into and through 90° elbow  40 , through conduit  42 , through secondary lint trap  46 &#39;s inlet collar  44 , and through mesh screen  96 —which traps lint. Lint-filtered exhaust air which passes through screen  96  flows through secondary lint trap  46 &#39;s outlet collar  48 , through conduit  50 , through 90° elbow  52 , into and through ceiling-embedded vent duct  54  which exhausts the air from the building. 
     After dryer  12  ceases operation, tray  58  can be slidably removed from housing  56  by grasping handle  100  and pulling tray  58  forwardly through frontal opening  60 . Any lint trapped on screen  96  is removed. Tray  58  is then slidably replaced within housing  56  to realign screen  96  between inlet and outlet collars  44 ,  48 . 
     As previously mentioned, a stackable laundry washer/dryer unit is often used to conserve space in a high-rise building suite. Sometimes, a relatively narrow closet is provided to house the washer/dryer unit. The closet may have insufficient room for mounting prior art secondary lint trap  16 A or  16 B in a conveniently accessible position within the closet. However, if prior art secondary lint trap  16 A or  16 B is mounted outside the closet, it may be necessary to use additional 90° elbows, or additional conduit, or both, to connect dryer  12 &#39;s exhaust outlet  18  through prior art secondary lint trap  16 A or  16 B to a building-embedded vent duct, thus exacerbating the aforementioned inefficient dryer operation problem. Secondary lint trap  46  overcomes these shortcomings because secondary lint trap  46  can be mounted inside a narrow closet in a conveniently accessible position atop a stackable laundry washer/dryer unit housed inside the closet. 
     While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof For example, although it may be convenient to mount housing  56  atop dryer  12 , housing  56  may alternatively be mounted above dryer  12  provided inlet and outlet collars  44 ,  48  extend rearwardly of dryer  12 &#39;s rear wall  88  to facilitate coupling of dryer  12 &#39;s exhaust outlet  18  through one 90° elbow to inlet collar  44  via one short, substantially straight, elbowless conduit; and facilitate coupling of outlet collar  48  through one other 90° elbow to vent duct  54  via another short, substantially straight, elbowless conduit  50 . As another example, although it may be convenient for handle  100  to protrude slightly forwardly of dryer  12 &#39;s front wall  104  when tray  58  is frilly inserted within housing  56 , handle  100  need only be sufficiently near front wall  104  to facilitate removal and reinsertion of tray  58  within housing  56 . It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.