Patent Publication Number: US-7722284-B1

Title: Traffic impact attenuator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     “Not applicable” 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     “Not applicable” 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     “Not applicable” 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     “Not applicable” 
     BACK GROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention relates generally to the traffic control system on the Freeway or Hiway where vehicles speed exceeding forty miles per hour. Vehicle accident at this speed level could create major damage to the vehicles and casualties to the occupants. 
     The concept behind “Traffic Impact Attenuator” is to prevent serious casualty and vehicle damages in case of lost control and run into guard rail or cushion drums at Freeway exit or median. 
     (2) Prior Art 
     Existing impact absorbing device installed on the Freeway ramps, is made of plastic drums installed in series up to five or six drums. Drums are filled with sand to secure drum movement and absorb impact from vehicles. This type of absorbing device is not affective and could cause more damage to vehicles and casualty to the vehicle occupants. 
     Each time after accident, clean up effort can take hours to move plastic debris and sand that spread all over the place on the traffic surface. If clean up effort can not be done promptly, sand on the surface can potentially cause more accident is due to slippage to the next vehicle exit at the same location. 
     “Traffic Impact Attenuator” after an accident can be restored to the same condition within a short period of time. Sliding tube can be moved to the previous location by pickup truck or human force. 
     “Traffic Impact Attenuator” is the right solution for this type of application that related to human lives and property lost in each of an accident. “Traffic Impact Attenuator” offers less impact force and required no clean up effort after an accident. Deceleration rate of the vehicle is far less than other drum type because of longer displacement prior to complete stop. As a result the impact exerted to the vehicle is drastically reduced relative to deceleration rate. 
     BRIEF SUMMARY OF THE INVENTION 
     The Traffic Impact Attenuator of the invention incorporates a rubber bumper and a guide tube, guide bearings, a clamp, a hold down T-rail, a telescopic shock absorber, a water tank with cover, a water level control valve, a drain valve and a rear support bracket. 
     A rubber bumper is mounted on a guide tube and the guide tube is interconnected to a telescopic shock absorber through a clamp. The guide tube has two guide bearings. The guide tube front end is restrained with hold down T-rail. 
     The telescopic shock absorber is encased in a water tank below guide tube. The telescopic shock absorber is filled up with water. the distal end of the telescopic shock absorber is mounted to the tank wall and supported by a rear support bracket. The support bracket is anchored to the concrete foundation. 
     The main cylinder of a shock absorber is provided with series of holes in difference sizes and arranged so that the largest hole is located closest to the main cylinder open end. Water inside the main cylinder moves freely from the main cylinder to the tank through passage holes in normal condition. Total cross section area of holes on cylinder wall is less than cross section area of the cylinder. 
     Water supply to the water tank is provided from an irrigation system or water truck. The water tank also has drain valve to empty the tank as required. 
     As a vehicle is accidentally crashed into the Traffic Impact Attenuator, the bumper absorbs some impact and begins sliding backwards along the guide. The impact energy is transferred from guide tube to the telescopic shock absorber. 
     The cylinder pressure is increasingly changed through out the movement of a piston. 
     Once the cylinder pressure overcomes impact force, the piston will stop prior to bottom out. If the impact force is greater than the force created by the pressure, the piston will move further to the end of the stroke. All the holes on the wall are overlapped by a piston. At this position the pressure inside the piston is drastically increased and brings the piston to stop. The impact force that is exerted to the cylinder rear end will be transferred to the foundation via rear support bracket. 
     The Traffic Impact Attenuator is a durable and maintenance free unit, the major immersed components to be made of stainless steel, PVC or fiberglass as required to prevent corrosion and sustain pressure. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Details of the invention will be clearly understood with reference to the followings: 
         FIG. 1  Side elevation cross section at normal position 
         FIG. 2  Side elevation cross section at fully retracted when hit by heavy vehicle. 
         FIG. 3  Plan view at normal position. 
         FIG. 4  Plan view at fully retracted position when hit by heavy vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings,  FIG. 1  discloses the embodiment of the invention for a Freeway Impact Attenuator. The rubber bumper  1  is connected to a rectangular guide tube front face  2 , guide tube hold down T-rail  3 , front guide bearing  5  and, 
     rear guide bearing  9 . 
     The guide tube  2  interconnected to a telescopic shock absorber piston  7  through a clamp  6 , the piston is housed in intermediate cylinder  8  and main cylinder  11  respectively. A main cylinder end cap is mounted to the water tank wall  8 . 
     The tank rear wall rests directly against rear support bracket  10  and is anchored to the footing  4  through anchor bolts  13 . 
     The rubber bumper  1  is arranged so that a vehicle bumper from 6 inches to 30 inches above ground surface can be intercepted. 
     As shown on the design, deceleration displacement of the vehicle is around 87 inches at this distance, the impact from vehicle is greatly reduced and prevent loss of life. 
     The deceleration displacement can be increased depending on space available. 
       FIG. 2  illustrates the embodiment of the invention for a Freeway Impact Attenuator in a side view, guard rails  14  are articulately connected to guide tube front face via pins and on the other ends are supported by steel posts  15 . Guard rails  16  are stationary parts and the posts  17  are the same as those used for the traffic control. 
     Water tank  18  is at least partially filled up with water which is to be used as shock absorber fluid that is located inside the tank. The water tank is enclosed with a cover to avoid contamination. Replenish and flow control valve  20  and drain valve  19  are provided to serve the purpose as required to maintain proper function of the system.