Patent Abstract:
A safety radiator cap has a centrally located pressure plunger that forces pins outward against the inside of a radiator fill tube to prevent opening of the cap when the system is under pressure. As the liquid cools, the pressure is reduced and the pins retract due to biasing springs which allow the cap to be removed thus ensuring that the cap can only be removed when safe. Pressure pads at the end of the pins allow an embodiment of the invention to be used in any vehicle without retrofitting.

Full Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority and herein incorporates by reference U.S. provisional patent application 60/885,553, filed Jan. 18, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The internal combustion engine has revolutionized the world we live in. Although some engines use air cooling techniques to control the temperature, most vehicles use liquid cooled systems that utilize a radiator filled with a liquid that circulates through a series of hoses and channels in the engine block designed to transfer heat away from the engine. There are basically two types of water cooling systems. The older system utilizes a non-pressurized radiator that operates at a temperature of approximately 180° F. The hot water from the engine is pumped through the radiator while airflow keeps the operating temperature constant. This means that while the system is operating properly, the water is kept below the boiling point, and therefore the radiator cap of such a system can be opened without significant risk of injury. Of course, even with this system, overheating can result in serious injury when trying to remove the radiator cap. 
         [0003]    Because of the thermodynamic advantage associated with greater temperature differences, most current liquid cooled systems operate with a pressurized radiator, allowing the coolant to remain a liquid above the atmospheric boiling point. Because of this, even in a properly operating system, it is extremely dangerous to remove the radiator cap until the coolant is been given sufficient time to cool down. In such systems, if the radiator cap is removed before cooling, the liquid will instantly vaporize in a dangerous explosion of steam. There is a need for a radiator cap that keeps a user from being injured when trying to access the cooling system of the vehicle. 
       SUMMARY OF THE INVENTION 
       [0004]    A safety radiator cap has a centrally located pressure plunger that forces pins outward against the inside of a radiator fill tube to prevent opening of the cap when the system is under pressure. As the liquid cools, the pressure is reduced and the pins retract due to biasing springs which allow the cap to be removed thus ensuring that the cap can only be removed when safe. Pressure pads at the end of the pins allow an embodiment of the invention to be used in any vehicle without retrofitting. 
         [0005]    Other features and advantages of the instant invention will become apparent from the following description of the invention which refers to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a cutaway view of an embodiment according to the present invention. 
           [0007]      FIG. 2  is a cutaway view of the embodiment shown in  FIG. 1  showing the safety pins engaged. 
           [0008]      FIG. 3  is a cutaway view of the embodiment according to the present invention showing the safety pin engaged with a specialized radiator fill tube. 
           [0009]      FIG. 4  is a perspective view of a radiator fill tube according to the present invention. 
           [0010]      FIG. 5  is a perspective view of the safety radiator cap engaged according to the present invention. 
           [0011]      FIG. 6  is a close up view of a section shown in  FIG. 5 . 
           [0012]      FIG. 7  is a cutaway view of another embodiment according to the present invention. 
           [0013]      FIG. 8  is a cutaway view of the embodiment shown in  FIG. 7  with safety pins engaged. 
           [0014]      FIG. 9  is a perspective view of a safety radiator cap according to the embodiment shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Reference is now made to the drawings in which reference numerals refer to like elements. 
         [0016]    Referring now  FIGS. 1 through 4 , a safety radiator cap  100  has a center slide  126  along which a pressure plunger  134  moves up and down in response to the pressure within a radiator (not shown). In the embodiment shown, at least two pins  118  are radially disposed within a channel in lower ring  122 , which guides pin  118  as it moves back and forth in response to pressure. At another end of pin  118  is a distally disposed pin follower  116 , which rides along an angled section of pressure plunger  134 . Disposed along a bottom portion of pressure plunger  134  is pressure plate  136 . 
         [0017]    Safety radiator cap  100  has a Portion  106  is held in place by a end holder  104  which is welded, bolted or glued to maintain integrity. An upper ring  102  applies pressure to an upper gasket  108  which is spring-loaded connection with outer spring  110 . As safety radiator  100  is pushed down on upper sealing seat  144  upper gasket  108  seals the cooling system accessible through radiator fill tube  140  by pushing against upper sealing ring  154  of radiator fill tube  140 . Safety radiator cap  100  is locked in place by locking tabs  158  fitting within locking cutouts  146  as is known in the art. In this embodiment, as soon as pressure begins to build within the cooling system, pressure plate  136  moves upward along center slide  126  overcoming center spring  114  which biases pressure plunger  14  in a non-locked position. Pressure plunger  134  has a sloped portion where pin followers  116  ride up and down causing them to move laterally in response to the pressure change within the cooling system. 
         [0018]    Pins  118  are biased in an unlocked position by pin springs  124  which are held in place by pin spring retainers  138 . A lower gasket  120  seals against a lower sealing ring  156  of radiator fill tube  140  during normal operation. In the event of an over pressurized condition, liquid and gas escapes by forcing lower ring  122  to move up so that the liquid and gas is released through overflow tube  142 . Pins  118  make contact with a locking ring groove  148  disposed within radiator fill tube  140  preventing safety radiator cap  100  from being removed until the cooling system is no longer under pressure. 
         [0019]    Pressure plunger  134  is biased in an un-locked condition by center spring  114  which pushes against a center housing  132  and is held in place by center spring retainer  112 . As the pressure decreases, center spring  114  forces pressure plunger  134  to move downwards which allows pins  118  to retract which in turn allows safety radiator cap  100  to be removed. This embodiment requires radiator fill tube  140  to be manufactured with locking pin ring  148 . 
         [0020]    Referring now to  FIGS. 5 and 6 , another embodiment of the safety radiator cap is shown having a conventional radiator fill tube  300  that lacks locking pin ring  148  ( FIG. 4 ). Pins  118  have pressure pads  152  mounted on their ends. As pins  118  are forced outward, pressure packed  152  deform against the inside surface of radiator fill tube  300 . Pressure pads  152  may be made of rubber or other high friction deformable material. As the pressure increases in the cooling system, safety radiator cap will be highly resistant to movement due to the pressure of pins  118  and pressure pads  152  being forced against the inside of radiator fill tube  300 . At the pressure is released, pins  118  will retract thus allowing safety radiator cap to be removed. 
         [0021]    Now referring to  FIGS. 7 ,  8  and  9 , another embodiment of the safety radiator  200  is shown having a stationary center slide to  234  mounted on a center support to  226 . In this embodiment, safety radiator  200  has a cap portion  206  held in place by an end holder  204 . Of course other means are acceptable to hold cap  206  in place thus eliminating the need for end holder  204 . Cap portion  206  encloses an upper ring  202  in contact with an upper gasket  208 . The cooling system is sealed when lower sealing ring  222  pushes against a sealing portion of a radiator fill tube (not shown). As the pressure increases within the system lower sealing ring  222  is forced up allowing liquid and gas to escape but also forcing pins  218  outward exerting pressure against an interior wall of radiator fill tube (not shown). 
         [0022]    Pins  218  move outward when pin followers  216  follow the angled surface of center slide  234  as lower ring  222  is forced upward due to pressure within the cooling system. Pressure pads  252  deform to apply frictional pressure making removal of safety radiator  200  difficult in an unsafe condition. Pins  218  are biased in an unlocked condition by pin springs  234  which are held in place by pin spring retainer  238 . Lower ring  222  is biased to normally seal the cooling system by spring  210  which moves upward in response to the pressure within the cooling system. A center housing  232  provides support for a center pin  226  which holds center slide  234  firmly in place. 
         [0023]    The amount of play that lower ring  222  has may be adjusted by appropriate selection of pin springs  224 . As the pressure builds, lower ring  222  begins to move upward releasing some pressure through an overflow tube (not shown). As the pressure begins to build more however, lower ring  222  will be forced to move further upward applying pressure through pins  218  making removal of safety radiator cap  200  more and more difficult as the pressure increases. 
         [0024]    Additionally, although the present invention is described in use with a radiator, it is easily adaptable for use with any pressurized application such as a hydraulic filling system, steam lines, etc. Also, some radiator systems do not have a user access cap as described above. Those systems use a pressurized overflow system that utilizes a fill cap attached to the overflow container rather than on the radiator directly. It is within the scope of this disclosure to include using the instant invention in such a system in the same way as described above with the difference being that the safety pressure cap fits within the overflow collar rather than the radiator directly. 
         [0025]    Although the instant invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art.

Technology Classification (CPC): 5