A spill-proof lid for use with a container for liquids includes a liquid chamber that has an outlet opening above and an inlet opening below the plane of the lid and a vent chamber, which has an inlet above and an outlet below the level of the lid. Each chamber's outlet and inlet ends are adjacent one another. However, the outlet and inlet ends of the vent chamber are on an opposite edge of the lid from the outlet and inlet ends of the liquid chamber. The chambers are constructed so that, as they extend from inlet to outlet, they traverse the lid from edge to axially opposing edge and back again. The periphery of the lid is constructed to sealingly engage the upper edge of the container. Preferably, the inlet end of the vent and the outlet end of the liquid chamber have mouthpieces formed thereon for ease of drinking. In one embodiment of the lid, the liquid and vent chambers are concentric single-loop helixes.

BACKGROUND OF THE INVENTION 
This invention relates to lids to cover containers for liquids, such as 
glasses and cups, and, more particularly, relates to a lid that prevents 
accidental spillage of the liquid within the container while allowing a 
person to drink the liquid from the container without removal of the lid. 
When liquids, such as coffee, tea, juice, and the like, are carried in cups 
or glasses in moving vehicles, such as airplanes, trains, buses, or cars, 
the irregular movement of the vehicle often causes the liquid to jiggle 
and splash within the container. The jiggling and splashing can cause the 
liquid to spill out of the container and over the hands and clothing of 
the person using the container or over the clothing of persons in the 
vicinity of the user. Also, if the container is set down by the user while 
the vehicle is moving, the motion of the vehicle may tip the container 
over, spilling the contents of the container. 
Many attempts have been made to provide a container and cover for 
preventing the splashing and spilling of liquids for use in moving 
vehicles; however, such attempts have resulted in cups, containers, and 
covers that are expensive to produce, difficult and cumbersome to use, and 
typically provide that the container and cup be made to accommodate one 
another so that a universal lid for use on many different types of 
containers has not been produced. An example of a container lid that 
attempts to solve the splashing problem is shown in U.S. Pat. No. 
4,394,928, issued July 26, 1983 to Morris Philip. The Philip lid addresses 
the problem of splashing of the liquid while the cup is in a vertical 
position; however, it does not address the problem of spillage of the 
liquid when the cup is tilted sideways. In fact, the Philip lid is 
designed to allow flow of liquid when the cup is tilted sideways. Also, 
the disclosure in Philip describes a cover and container that are 
constructed to cooperate with one another so that the cover can only be 
used on the matching container and is not a universal cover for use with 
many different types of containers. Likewise, the covers shown in U.S. 
Pat. Nos. 4,322,014 and 3,915,355 also deal with the splashing problem but 
not the problem of spilling of the liquid from the container when the 
container is in a horizontal position. 
It is, therefore, an object of the present invention to provide a lid for a 
container to prevent spilling of liquid from the container when the 
container is in a horizontal or even inverted position and to prevent 
splashing of the liquid from the container when the container is in a 
vertical position. 
Another object of the invention is to provide such a lid that is able to be 
used with standard containers and does not need a customized container to 
be adapted to it. 
Another object of the invention is to provide such a lid that is relatively 
simple and inexpensive to manufacture. 
SUMMARY OF THE INVENTION 
In accordance with the above-stated objects, the present invention provides 
a spill-proof lid for use with a container for liquids. The lid includes a 
cover plate for covering the open end of the container. The periphery of 
the plate is constructed to sealingly engage the upper edges of the walls 
of the container in a conventional manner to provide a spill-proof 
attachment between the lid and the container. The lid includes a first 
liquid chamber that has an inlet end that opens below the lower surface of 
the plate so that it is in fluid communication with the interior of the 
container and an outlet end that opens above the upper surface of the 
plate so that it is in fluid communication with the environment outside 
the container. The inlet and outlet of the liquid chamber are closely 
adjacent one another and located near an edge of the plate. As the chamber 
extends from the inlet to the outlet it traverses the lid to a point near 
an opposite edge of the lid, axially opposed to the location of the inlet 
and then traverses the lid again to the outlet. The chamber can follow a 
curvilinear path to improve user comfort and lid function. The lid also 
includes a vent chamber that has an inlet end in communication with the 
environment outside the container and an outlet end that is in 
communication with the interior of the container. The inlet and outlet of 
the vent chamber are also located adjacent one another but are on an 
opposite edge of the plate from the inlet and outlet of the liquid 
chamber. The path that the vent chamber follows as it extends between its 
inlet and outlet runs from the inlet to a point on the edge of the plate 
opposite the inlet and back to the outlet. 
The operation of the cup and lid is such that the basic plate provides 
splash protection when the cup is in the upright position. When the cup is 
tilted in the direction of the inlet of the liquid chamber, liquid moves 
toward the lid and the inlet of the liquid chamber. The liquid enters the 
inlet of the liquid chamber and rises up the chamber. Due to the liquid 
seeking its own level, the fluid rises in the chamber only until it is at 
the same level with the liquid in the container. The fluid cannot rise 
above this level until the user applies a suction with his mouth. The user 
places his mouth over the outlet opening of the liquid chamber and 
produces a suction of the chamber much like drinking with a straw. The 
liquid is moved through the chamber from the inlet to the outlet by the 
suction applied by the user. At the same time, air from outside the 
container enters the vent chamber inlet and prevents a vacuum from forming 
within the container. When the cup is tipped over with no suction being 
applied by the user, for example, if it is accidentally knocked over, 
liquid may fill a portion of either or both the vent chamber and the 
liquid chamber; however, the liquid in either chamber will not rise above 
the level of liquid in the cup and will not reach the other ends of the 
chamber. With violent shaking, a few drops of liquid may be forced out, 
but no more. 
The design continues to be spill-proof even when the container is inverted. 
As the container is tipped, the fluid level rises up the inlet side of the 
liquid chamber, maintaining the same level as the level of the liquid in 
the container. As the container passes the horizontal position, the air 
within the container rises to the container bottom, which is now at a 
level above the lid. Once the liquid has risen in the container 
sufficiently to cover the lid's lower surface and partly fill the liquid 
chamber, the liquid will still not exit the container, since the vent will 
also be blocked by liquid and atmospheric pressure will keep the liquid 
locked in the container. 
Preferably, in one embodiment of the lid, the liquid chamber is larger than 
the vent chamber. In the illustrated embodiment, the liquid chamber is a 
single-loop helix that descends from the outlet to the inlet with the 
container in an upright position and the vent chamber is a similar 
single-loop helix, concentric with the liquid chamber, that also descends 
downwardly from the vent inlet to the vent outlet with the cup in the 
upright position. The reason for using the ramped configuration is to 
eliminate inconveniences present if the chambers are formed in a flat 
plane. If a user tips the container and draws on the liquid chamber 
outlet, extracting liquid from the container, and then stops drinking and 
tilts the cup upright, a certain amount of liquid is held in the chamber 
by surface tension at the inlet. As the user then tips the cup to drink 
again, the trapped liquid in the chamber can dribble out the outlet before 
the user gets the cup to his mouth. In order to cure this inconvenience, 
the chamber is designed with a "downhill" component so that each time the 
user tips the container back to an upright position after drinking, the 
liquid will drain out of the chamber and into the container. 
Another potential inconvenience addressed by the illustrated embodiment is 
one most likely to be encountered with the lid used by an infant or young 
child. With certain configurations of the chambers, a siphon can 
accidentally be created by sucking liquid through the chamber and taking 
the container away from the mouth without righting the container. The 
single-loop helix with its "downhill" component is one configuration that 
prevents the accidental siphon effect by forcing the liquid to return to 
the container whenever suction is removed.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
FIG. 1 shows one embodiment of a spill-proof lid for a container of liquid 
made in accordance with the principles of the present invention. The lid 
includes a disk-shaped plate 10 that has an outer periphery 12 formed in a 
conventional manner so that it is capable of sealingly engaging the upper 
edge of the wall of a conventional cylindrical cup or glass. The lid also 
includes a liquid chamber 14 that is formed in the shape of single-loop 
helix that has a first outlet end 16 that opens above the disk 10 and 
descends downwardly and terminates at a second inlet end 18 located below 
the level of the disk 10 but radially closely adjacent the first outlet 
end 16. The liquid chamber 14 is a closed tube, except for its two ends. A 
vent chamber 20 is also a single-loop helix that begins at a first inlet 
end 22 located above the plate 10 and diametrically opposite the first end 
16 of the liquid chamber 14. The vent chamber 20 then also descends in 
helical fashion to its terminus at a second outlet end 24 located below 
the plane of the plate 10 and radially closely adjacent the first inlet 
end 22 of the vent chamber. The embodiment of the lid pictured in FIGS. 1 
and 2 shows raised mouth portions 26 and 28, formed, respectively, on the 
first outlet end 16 of the liquid chamber 14 and the first inlet end 22 of 
the vent chamber 20. 
FIG. 2 is an exploded isometric view of the lid of FIG. 1 showing the lid 
as constructed in two sections, the first section 10a including the first 
ends of both the liquid chamber 14 and the vent chamber 20, and the lower 
portion 10b including the second ends of the vent chamber 20 and the 
liquid chamber 14. Approximately one-half of each of the chambers is 
located in the upper and lower portions, respectively, so that when they 
are joined together the continuous tubular liquid chamber 14 and the 
continuous tubular vent chamber 20 are formed. 
In operation, a user would place the lid over the open end of a container 
and, when he desired to drink from the container, he would place his lips 
over the first outlet end 16 of the liquid chamber 14 and produce a 
suction with his mouth, tilting the cup so that the liquid was adjacent 
the second inlet end 18 of the liquid chamber. The sucking action by the 
user would act to move the liquid through the liquid chamber 14 and into 
the mouth of the user, much like the action of a straw. At the same time, 
air would be able to enter the container through the inlet 22 of the vent 
chamber to prevent a vacuum from forming within the container. The major 
benefit of the lid of FIGS. 1 and 2 is that when the cup is in a 
horizontal position, such as if it were accidentally knocked on its side, 
liquid would enter the second inlet end 18 of the liquid chamber 14 and 
the second outlet end 24 of the vent chamber 20, but would only rise 
within the respective chambers to a level the same as the level of liquid 
within the cup. The liquid will not fill the entire length of either of 
the chambers and, therefore, will not be able to exit the cup. Thus, 
spilling of the liquid is prevented, except for some minor spillage that 
may occur from liquid that may have already been contained within one of 
the chambers when the cup was tipped over. Due to the descending helical 
configuration of the chambers, any liquid in the chambers will drain back 
into the cup each time the cup is placed in the upright position, so even 
minor spillage is eliminated. 
In the preferred embodiment pictured in FIGS. 1 and 2, the liquid chamber 
14 is larger in cross section than the vent chamber 20 and the inlet 
opening at the first end 22 of the vent chamber is smaller than the outlet 
opening at the first end 16 of the liquid chamber. In a situation where 
the liquid within the container is of comfortable temperature, typically, 
the user would use the larger opening in the larger chamber in order to 
obtain more liquid in a shorter time from the cup. However, if the liquid 
within the container were too hot to be comfortably drunk, the smaller 
vent chamber 20 could actually be used to extract liquid from within the 
container in smaller quantities so that the user does not burn his mouth. 
Also, the helical path that the liquid must follow as it exits the 
container provides some radiational cooling of the liquid as it travels 
through the chamber so that the liquid exiting the vent chamber would be 
at least somewhat cooler than the liquid entering the chamber directly 
from the container. The use of the terms "liquid" and "vent chamber" and 
the designation "inlet" or "outlet" for each end of the respective chamber 
is therefore arbitrary and, in fact, the chamber 20 can be used to extract 
liquid and the chamber 14 used to vent the container, if the user so 
desires. 
FIGS. 3 and 4 show a second embodiment of the invention that is very 
similar to the first embodiment, except in the configuration of the 
mouthpiece 26' at the first end 16' of the liquid chamber 14' and the 
elimination of any mouthpiece at the first end 22' of the vent chamber 
20'. It can be seen that the mouthpiece 26' at the first end of the liquid 
chamber 14' is longer and extends higher above the lid, while the opening 
at the first end 22' of the vent chamber 20' is simply a hole 28' formed 
in the plate 10a'. The lid of FIGS. 3 and 4 is intended for use as a lid 
for a baby's cup and the tall mouthpiece 26' makes it easier for the baby 
to extract liquid by placing its mouth over the mouthpiece 26'. The lack 
of a second mouthpiece means that the baby will use the liquid chamber 
mouthpiece exclusively and will not have to make a decision as to which 
mouthpiece to use. Typically, the liquids in a baby's cup would be tested 
by one of its parents prior to consumption by the baby and, therefore, the 
advantage of hot and cold alternatives for drinking out of the cup is not 
as important. 
While preferred embodiments of the invention have been discussed and 
illustrated, it should be understood by those of ordinary skill in the art 
and others that changes can be made to the illustrated embodiments without 
departing from the spirit and scope of the present invention. For example, 
while circular lids are shown, it would be possible to utilize the 
principles of this invention with a lid that was square or rectangular or 
of other geometrical shape. Also, while the chambers are essentially 
circular in plan view, any shape can be used as long as the chamber 
extends from one edge of the lid, across the lid, and back again to 
achieve the spill-proof characteristics. While the illustrated liquid 
chambers descend from the outlet to inlet ends, it would be possible to 
have the chambers in a flat plane as well. Also, while the lid is shown as 
being constructed of two separate pieces, the operation of the lid would 
not be affected if it were constructed in one single piece, although that 
would most likely involve complex manufacturing processes. Since such 
changes can be made to the illustrated embodiments while remaining within 
the scope of the invention, the invention should be defined solely with 
reference to the appended claims.