Fuel tank level indicator

A fuel tank level indicator for indicating at a surface when a fuel tank is filled with fuel, such indicator installed on a fuel inlet pipe and having a loop pipe in line with the inlet pipe with a riser pipe at the top of the loop and a float member disposed in the riser pipe to raise an indicator member above the surface when the loop pipe fills with fuel. The fuel is prevented from backing up the inlet pipe by a back flow preventor and some of the fuel then passes into the riser pipe, raising the float member and its attached indicator member above the surface where it is visible by the person entering fuel into the inlet pipe who will then see the indicator member and stop the flow of fuel.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The device of this invention resides in the area of fluid level indicators 
and more particularly relates to a device with means to indicate when a 
boat's fuel tank is full. 
2. Description of the Prior Art 
Prior art boat fuel tanks often have a fuel inlet on the boat's deck with 
no means to gauge when the fuel tank is full. When the tank is being 
filled with fuel, excess fuel beyond the fuel tank's capacity can often 
overflow onto the deck. Some boats have an overflow pipe that is 
positioned on the side of the hull and when the fuel tank is overfilled, 
the excess fuel is allowed to spill out into the water surrounding the 
boat which spillage causes undesirable pollution and creates a fire 
hazard. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a device which is incorporated 
into the fuel inlet pipe extending down to a fuel tank such that as the 
fuel tank fills with fuel, the device visually indicates when the fuel 
tank is full without any of the fuel spilling onto the deck or into the 
surrounding water. 
It is a further object of this invention to provide a fuel tank level 
indicator which is easy to utilize and convenient to maintain. 
The device of this invention is used in conjunction with a fuel inlet pipe 
wherein the inlet pipe extends first down and then around in a reverse 
circular loop. The fuel passes through the loop on its way to the fuel 
tank. At the top of the loop is located a riser pipe which can be vented 
if desired and which extends up to the surface of the deck. At the top of 
the riser pipe is a movable indicator member, the movement of which is 
controlled by the upward and downward movement of a float rod which is 
attached at one end to the indicator member and at the other end to a ball 
float member which is disposed at the bottom of the riser pipe. The riser 
pipe is connected to an aperture defined at the top of the loop formed in 
the fuel inlet pipe. A back flow preventor is located in the fuel inlet 
pipe at approximately the same level as the level of the riser pipe's 
attachment to the loop. As fuel enters the fuel inlet pipe, it passes by 
the back flow preventor. When the fuel backs up in the fuel inlet pipe 
sufficiently to reach the level of the back flow preventor, the back flow 
preventor closes, thereby preventing any fuel from rising further up the 
fuel inlet pipe. The fuel, though, which by then has risen within the 
loop, passes up into the bottom of the riser pipe, causing the ball float 
member located at the bottom of the riser pipe to rise. Since the diameter 
of the riser pipe is narrower than the diameter of the fuel inlet pipe, 
only a small amount of fuel which moves by pressure past the backflow 
preventor is needed to cause the ball float member and its attached float 
rod to rise within the riser pipe and push the indicator member above the 
surface of the deck, visually indicating to the person filling the fuel 
tank that the fuel tank is full.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
FIG. 1 illustrates a side view of the structure of the fuel tank level 
indicator 10 of this invention wherein the surface of deck 12 of a boat is 
seen. It should be noted that although the structure has been illustrated 
in conjunction with a boat deck, the structure of this invention can be 
used in conjunction with other fuel inlet pipes which are disposed in 
similar relationship to any upper surface. The structure of this invention 
is not solely limited in its use to boat fuel inlet pipes. 
Seen in FIG. 1 is cap 14 which covers the fuel inlet pipe. When fuel is to 
be entered into the fuel tank, cap 14 is first removed from the top of the 
upper portion of gas tank inlet pipe 16, and a typical fuel-dispensing 
nozzle, not shown, is inserted in inlet pipe 16 to dispense fuel therein. 
The fuel passes by back flow preventor 18 and into inlet pipe loop 24 
which causes the fuel to go through inlet pipe loop 24 in a reverse 
circular path and continue downward in lower portion 42 of the fuel inlet 
pipe which extends downward to the fuel tank, not shown. The structure of 
this invention utilizes inlet pipe loop 24 in fluid communication with 
riser pipe 28 which extends upward from its point of attachment 26 located 
near the top of inlet pipe loop 24. After the tank is filled with fuel, 
the fuel backs up through lower portion 42 of the inlet pipe and passes 
around top portion 22 of inlet lower portion 42 of the inlet pipe and 
passes around top portion 22 of inlet pipe loop 24 and fills the bottom 
portion 20 of inlet pipe loop 24. Inlet pipe loop 24 fills with fuel and 
eventually inlet pipe 16 will also fill with fuel up to back flow 
preventor 18 which prevents any fuel from backing up into the upper 
portion of inlet pipe 16. Back flow preventor in one embodiment can have a 
flap 19 movable on hinge 21 urged by spring 23 against stop member 25. The 
force of fuel on the top of flap 19 opens back flow preventor 18, but fuel 
backing up inlet pipe 16 causes flap 19 to move upward against stop member 
25 and stop any upward rising of fuel in inlet pipe 16. At this point a 
small amount of fuel, still entering under pressure and passing by back 
flow preventor 18, fills inlet pipe loop 24 and starts to progress up 
riser pipe 28. As the fuel rises in riser pipe 28, float member 30 floats 
and rises with the level of the rising fuel and causes the upward movement 
of float rod 32 which is attached to the float member. Float rod 32, in 
turn, is attached to indicator member 36 which is then raised by the 
upward movement of rising float rod 32 above indicator member deck mount 
38 such that indicator member 36 pops up above the deck's surface and can 
be seen on the deck's surface, indicating to the person filling the fuel 
tank that the fuel tank has been filled. Upon seeing the indicator member 
above the deck's surface, the person then stops the flow of fuel. The 
indicator member can have imprinted thereon the letters "FULL" or can be 
colored red or some other bright color so that the indicator member can be 
easily seen when it pops up from indicator member deck mount 38. Means, 
such as baffle member 34, can be positioned at the bottom of indicator 
member 36 to prevent fuel from passing beyond the bottom of indicator 
member 36 and inadvertently spilling out onto the surface of the deck. By 
the use of the fuel level indicator device 10 of this invention, one can 
prevent inadvertent spillage of fuel on the deck and subsequently into the 
surrounding water to avoid pollution thereof. 
Although the present invention has been described with reference to 
particular embodiments, it will be apparent to those skilled in the art 
that variations and modifications can be substituted therefor without 
departing from the principles and spirit of the invention.