Backflow prevention device for bathroom air duct

Abstract

A backflow prevention device is connected to a bathroom air duct and includes a case having two opposite gas inlet-end opening and gas outlet-end opening; a gas inlet-end unit and a gas outlet-end unit respectively mounted to and communicating with the gas inlet-end opening and the gas outlet-end opening; and at least one backflow prevention unit mounted in the case. The backflow prevention unit includes a frame and a plurality of baffle plates pivotally mounted in the frame. The baffle plates are arranged in the frame from top to bottom to overlap with each other, and can be pivotally turned only in one way toward the gas outlet-end opening to an open position. Thus, gas in a bathroom is allowed to flow from the gas inlet-end opening to the gas outlet-end opening, while gas with bad odor in a public pipe shaft is prevented from flowing back into the bathroom.

1 . A backflow prevention device for bathroom air duct, being connected to an air duct which is communicating with a bathroom and led to external facilities, comprising:
 a case internally defining a receiving space, two opposite ends of the receiving space separately defining a gas inlet-end opening and a gas outlet-end opening;   a gas inlet-end unit being mounted to and communicating with the gas inlet-end opening of the case;   a gas outlet-end unit being mounted to and communicating with the gas outlet-end opening of the case; and   at least one backflow prevention unit being mounted in the receiving space, and including:
 a frame defining an internal space; and 
 a plurality of baffle plates being pivotally connected to the frame to locate in the internal space; the baffle plates being arranged in the frame from top to bottom with an upper one overlapping an adjacent lower one, and being pivotally turnable only in one way toward the gas outlet-end opening of the case to an open position. 
   
   
   
       2 . The backflow prevention device for bathroom air duct as claimed in  claim 1 , wherein the frame of the backflow prevention unit includes two opposite upper and lower side boards, and two opposite left and right side boards; each of the plurality of baffle plates including a plate body and a shaft, the plate body having an upper edge portion and a lower edge portion opposite to the upper edge portion, and the shaft being located at the upper edge portion with two opposite ends of the shaft separately projected from two lateral ends of the plate body to pivotally connect to the left side board and the right side board. 
   
   
       3 . The backflow prevention device for bathroom air duct as claimed in  claim 2 , wherein each of the baffle plates includes a gas inlet-end surface and a gas outlet-end surface, which are opposite to each other and face toward the gas inlet-end opening and the gas outlet-end opening of the case, respectively; and wherein the lower edge portion of the plate body is formed into an outward bent cover portion, such that the outward bent cover portion of one upper plate body overlaps and covers an area of the gas outlet-end surface of an adjacent lower plate body at the upper edge portion thereof. 
   
   
       4 . The backflow prevention device for bathroom air duct as claimed in  claim 3 , wherein, on each of the baffle plates, the gas outlet-end surface at the upper edge portion is formed into an outer slope, and the gas inlet-end surface at the outward bent cover portion at the lower edge portion is formed into an inner slope. 
   
   
       5 . The backflow prevention device for bathroom air duct as claimed in  claim 4 , further comprising an inner frame provided in the internal space of the frame at a position facing toward the gas inlet-end opening of the case. 
   
   
       6 . The backflow prevention device for bathroom air duct as claimed in  claim 5 , wherein the frame is provided on outer faces thereof with a leak-preventive gasket packing. 
   
   
       7 . The backflow prevention device for bathroom air duct as claimed in  claim 5 , further comprising a first spacing frame provided in the receiving space of the case to locate at one side of the backflow prevention unit facing toward the gas outlet-end opening. 
   
   
       8 . The backflow prevention device for bathroom air duct as claimed in  claim 5 , wherein the gas inlet-end unit includes a gas inlet-end plate and a gas inlet pipe connected to and communicating with the gas inlet-end plate; and the gas inlet-end plate being mounted to the gas inlet-end opening with the gas inlet pipe communicating with the gas inlet-end opening. 
   
   
       9 . The backflow prevention device for bathroom air duct as claimed in  claim 5 , wherein the gas outlet-end unit includes a gas outlet-end plate and a gas outlet pipe connected to and communicating with the gas outlet-end plate; and the gas outlet-end plate being mounted to the gas outlet-end opening with the gas outlet pipe communicating with the gas outlet-end opening. 
   
   
       10 . The backflow prevention device for bathroom air duct as claimed in  claim 5 , further comprising a fan unit provided in the receiving space of the case to locate at a position facing toward the gas inlet-end opening. 
   
   
       11 . The backflow prevention device for bathroom air duct as claimed in  claim 10 , further comprising a second spacing frame located in the receiving space of the case at one side of the fan unit facing toward the gas outlet-end opening.