Air and vacuum relief valve

An air and vacuum relief value having a cylindrical housing defining a chamber and an aerodynamically shaped float body disposed for movement within said chamber between a lower, open position and an upper closed position, the float body having a generally inverted pear-shape configuration to prevent premature valve closure.

BACKGROUND OF THE INVENTION 
This invention relates to air and vacuum relief valves, and more 
particularly to a new and improved air and vacuum relief valve primarily 
intended for use in venting air to and from an irrigation water supply 
line. 
In many pressurized water supply lines such as, for example, those used in 
irrigation, it is highly desirable to prevent the formation of air blocks 
in the line by venting air from the line during filling of the system. On 
draining of the system, it may also be desirable to vent air back into the 
supply line to prevent the formation of a vacuum in the line which could 
cause the line to collapse. 
Various air vent and vacuum relief valves have been proposed in the prior 
art to protect against air blockage and vacuum collapse of a water supply 
line. Typically such prior art valves include a housing connected to the 
high point of the water supply line and within which is mounted a 
cylindrical or sphirical float body. On filling of the line, air is vented 
from the line through the valve until water enters the housing and raises 
the float body to close the valve. On draining of the line, water within 
the housing recedes, causing the float body to drop and open the valve for 
admitting air back into the line. 
While such prior art valves have met with some degree of commercial 
success, none has been totally satisfactory. One significant problem that 
has been encountered is that of pre-mature valve closure caused by high 
air flow rates through the valve on line filling. In many prior art 
valves, the float body is relatively light in weight and has a right 
cylindrical or sphirical shape presenting a relatively high coefficient of 
drag. With such float bodies, high air flow rates through the valve may 
prematurely lift the float body and close the valve before all air has 
been vented from the supply line. Although attempts have been made to 
design a valve that will not prematurely close due to high flow rates, 
such as valves have typically required baffles and shields which are 
expensive to manufacture and complex in design. 
Thus, there exists a need for a reliable and effective air and vacuum 
relief valve which is simple in design and economical to manufacture yet 
which will not prematurely close in the presence of high air flow rates 
through the valve. As will become more apparent hereinafter, the present 
invention satisfies this need. 
SUMMARY OF THE INVENTION 
The present invention provides a new and improved float body for an air and 
vacuum relief valve which is formed with an aerodynamically improved shape 
to reduce its coefficient of drag and which cooperates with the valve 
housing to operate in a highly reliable manner to insure proper valve 
closure once all air has been vented from the supply line, yet prevents 
premature valve closure as a result of high air flow rates through the 
valve. Moreover, the float body of the present invention is relatively 
economical to manufacture and simple in design, yet is very effective in 
operation. 
The float body is formed as a hollow, generally inverted pear-shaped shell 
with a lower, relatively small diameter bulbous nose portion and an upper, 
generally cylindrical portion of larger diameter joined with the lower 
portion by a downwardly and inwardly contoured smooth sidewall. The float 
body is supported for vertical movement within a housing chamber by a 
vertical shaft which is dimensioned to support the float body in the fully 
open position such that the smallest area passageway through which air 
moves from the valve inlet to the outlet is adjacent the chamber inlet and 
opposite the contoured sidewall. With this arrangement, any tendency for 
the air flowing through the valve body to raise the float due to passing 
through the construction will result in lifting of the float and an 
increase in the size of the constructing passageway, thereby reducing the 
lifting effect and arresting upward movement of the float. 
Moreover, due to the shape of the float body, the float body has a 
relatively large buoyancy thereby permitting weight to be added to the 
float to further inhibit premature closing due to high air flow rates 
while insuring that proper and effective valve closure takes place upon 
water entering the chamber. By increasing the buoyancy and effective 
weight of the float body, and tendency of the valve to stick in the closed 
position is also eliminated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
As shown in the exemplary drawings, the present invention is embodied in a 
new and improved air and vacuum relief valve 10 primarily intended for use 
in preventing air blocks and vacuum formation in a pressurized water 
supply line. Typically, such valves 10 are placed at the high point of a 
water supply line (not shown) such as those used in irrigation water 
supply systems to vent air from the line on initial filling, and to permit 
air flow back into the line upon draining. 
In this instance, the valve 10 includes a tubular housing 12, preferably 
formed of cast metal, having a lower portion 14 defining an inlet 
passageway 16 with a bottom inlet opening 18, and an upper portion 20 
forming an outlet passageway 22 with the laterally directed outlet opening 
24. A central cylindrical chamber 26 is formed between the inlet 
passageway 16 and the outlet passageway 22 by an enlarged diameter housing 
central portion 28, and a valve seat 30 is formed between the upper end of 
the chamber and the outlet passageway. The lower portion 14 of the housing 
12 is herein formed with internal threads 32 for coupling the valve 10 to 
a supply line, the supply line typically having a short vertical riser 
pipe (not shown) projecting from its upper sidewall for permitting fluid 
to communicate between the valve and the supply line. 
Disposed concentrically with the chamber 26 is a float body 34 coupled to a 
shaft 36 projecting upwardly through the upper portion 20 of the housing 
12 to a position outside the housing. The float 34 is supported by the 
shaft 36 for limited vertical movement between a lower, fully open 
position as shown in FIG. 1, and an upper closed position as shown in FIG. 
3. 
The shaft 36 herein is slidably supported by a cylindrical guide bearing 38 
secured in a hole 40 through the housing 12, the guide bearing having a 
central bore 42 which slidably engages the shaft to support and guide the 
shaft during movement of the float 34. Attached to the upper end of the 
shaft 36, herein by a transverse pin 44, is a knob shaped weight 46 which 
functions to limit downward movement of the shaft by abutting against the 
upper and the guide bearing 38, and to bias the float 34 toward the open 
position, and to assist in resisting lift generated by high air flow rates 
tending to prematurely close the valve. 
In accordance with the present invention, the float 34 is formed to have an 
aerodynamically improved shape to reduce its drag coefficient in the 
presence of air flow between the inlet 18 and the outlet 24, and 
cooperates with the housing 23 to operate in a highly reliable manner to 
insure proper closure of the valve 10 while preventing premature valve 
closure as a result of high flow rates through the housing. Moreover, the 
float 34 is relatively simple in design and economical to manufacture yet 
is highly effective in use. 
Toward the foregoing ends, the float 34 is formed as a hollow, air tight 
shell having the general shape of an inverted pear with a lower, 
relatively small diameter bulbous nose portion 48 and an upper cylindrical 
portion 50 of larger diameter joined with the lower portion by a generally 
smooth, downwardly and inwardly contoured sidewall portion 52. Preferably, 
the float 34 is formed of several molded plastic sections which are then 
welded or otherwise bonded together to form the airtight shell with air 
filling the internal volume of the float. 
Attached in overlying relation to the upper end of the upper portion 50 of 
the float 34 is a generally inverted cup-shaped cap 54 of reduced diameter 
having a centrally disposed upstanding boss 56 to which the lower end of 
the stem 36 is secured. As can best be seen in the sectional portion of 
FIG. 2, the cap 54 and upper end of the upper portion 50 of the float 34 
are formed to define a circumferential groove 58 into which is snap-fit a 
toridal shaped seal gasket 60 whose external diameter is generally the 
same as that of the upper portion. Preferably, the seal gasket 60. is made 
of elastomeric material, and operates to seat against the valve seat 30 
and form a fluid tight seal when the float is in the closed position. 
Importantly, the length of the shaft 36 is selected such that when the 
valve 10 is in the fully open position with the weight 46 stopped against 
the top of the guide bearing 36, the float is positioned with the bulbous 
nose portion 48 extending into the inlet passageway 16 and the contoured 
sidewall portion 52 disposed adjacent the internal junction 62 of the 
housing lower portion 14 and housing central position 28. In this portion, 
a restrictive annular space designated generally "d" is defined between 
the contoured sidewall portion 52 and the internal junction 62, and 
through which air must initially pass from the inlet 18 to the chamber 26. 
During high air flow conditions as may occur on rapid filling of the supply 
line, air flowing through the restrictive annulus "d" may tend to lift the 
float 34 toward the closed position. However, as can be seen in FIG. 2, 
premature lifting of the float 34 will result in an increase in the size 
of the annular space "d'", thereby reducing the air throttling effect and, 
hence, the tendency of the air to further lift the float. In this manner, 
any tendency for high air flow rates to permaturely lift the float 34 and 
close the valve 10 is significantly reduced. Moreover, the improved 
aerodynamic shape of the float 34 and the downward bias of the weight 46 
further reduce the tendency of the float to prematurely lift in the 
presence of high air flow rates. With these factors coupled together, the 
valve 10 is substantially prevented from premature closure due to high air 
flow rates through the housing 12. 
Once all undesireable air has been exhausted through the outlet 24, water 
from the supply line will rise through the inlet passageway 16 into the 
chamber 26. Due to the buoyancy of the float 34, as the water level within 
the chamber 26 rises, the float 34 also rises against the bias of the 
weight 46 until the seal gasket 60 engages the valve seat 30 and seals off 
the chamber from the outlet passageway 22, as can be seen in FIG. 3. On 
draining of the supply line, water recedes from the chamber 26 permitting 
the float 34 to move downwardly under the bias of the weight 46, thereby 
opening the valve 10 and permitting air to bleed back into the supply 
line. 
Thus, the present invention provides a new and improved air and vacuum 
relief valve 10 which substantially eliminates the problem of premature 
valve closure due to the high air flow rates through the valve. Moreover, 
due to the relatively high buoyancy of the float body 34, increased weight 
can be used to bias the float toward the open position thereby insuring 
that the float will not stick in the closed position and to assist in 
resisting lift generated by high air flow rates tending to prematurely 
close the valve, yet without impairing proper valve operation. 
While a particular form of the present invention has been herein 
illustrated, and described, it will be apparent that various modifications 
can be made without departing from the spirit and scope of this invention.