Information
-
Patent Grant
-
6254351
-
Patent Number
6,254,351
-
Date Filed
Tuesday, January 25, 200024 years ago
-
Date Issued
Tuesday, July 3, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Thorpe; Timothy S.
- Gray; Michael K.
-
CPC
-
US Classifications
Field of Search
US
- 417 40
- 200 84 R
- 200 84 B
- 073 313
- 074 971
-
International Classifications
-
Abstract
A float assembly for use in actuating a switch based on the level of a fluid includes a pivot member having a pivot axis and a switching surface. First and second floats are coupled to the pivot member so that at a first fluid level the first and second floats lie on different sides of a vertical line extending through the pivot axis and the switching surface causes the switch to assume a first switching state. At a second fluid level, the first and second floats lie on the same side of the vertical line extending through the pivot axis and the switching surface causes the switch to assume a second switching state.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to float assemblies for sensing fluid levels and, more particularly, to a float assembly for actuating a switch.
2. Background Art
Conventional float assemblies for actuating a switch based on a fluid level typically include a pushrod that extends upwardly from a float and which moves vertically with the float in response to changes in the fluid level. The pushrod may actuate the switch directly or, alternatively, may actuate the switch via an intermediate lever.
In applications where the float assembly controls the operation of a pump, it is desirable to provide switching hysteresis or a control deadband that allows the pump motor to cycle between on and off operational states at an acceptable frequency and duty cycle. As is commonly known, without switching hysteresis, electrical noise or high flow rates into the pumped container may cause the pump motor to cycle rapidly between on and off states when the fluid level is near the switching point. Such rapid cycling of the pump motor can substantially increase power consumption and shorten the life expectancy of the pump motor. It is further desirable to provide a positive (i.e., substantially bounceless) switching action because mechanical bouncing of the switch contacts may cause the pump motor to be turned on and off rapidly despite any switching hysteresis or control deadband and may cause premature wear and failure of the switch contacts.
Some conventional float assemblies provide a control deadband by coupling the float pushrod to the switch via a lost motion connection, which allows the vertical displacement of the float to change over a predetermined range of fluid levels without causing any actuation of the switch. Additionally, many of these conventional float assemblies also incorporate an electrical switch having a snap-acting or detent mechanism to provide a positive switching action that eliminates or minimizes contact bounce.
In one known configuration illustrated in
FIG. 1
, a conventional float
10
follows the level of a fluid within a tank
12
. A pushrod
14
extends coaxially from the float
10
and is coupled to the float
10
so that the pushrod
14
follows the vertical displacement of the float
10
. The pushrod
14
passes freely through an opening (not shown) in a lever arm
16
which is coupled to a detent switch
18
. The pushrod
14
includes an upper pushnut
20
and a lower pushnut
22
that define a control deadband therebetween. This control deadband allows the pushrod
14
to move vertically through the lever arm
16
a predetermined distance without actuating the lever arm
16
or the detent switch
18
.
At a low fluid level
24
, the pushrod
14
is retracted into the tank
12
so that the upper pushnut
20
pulls the lever arm
16
downward to cause the detent switch
18
to be in one of two switching states. Similarly, at a high fluid level
26
, the pushrod extends out of the tank
12
so that the lower pushnut
22
pushes the lever arm
16
upward to cause the detent switch
18
to be in the other one of the two switching states.
While the float assembly shown in
FIG. 1
establishes a control deadband so that a pump motor controlled by the detent switch
18
is turned on at one fluid level and turned off at another fluid level, the structure of
FIG. 1
is relatively expensive to manufacture because it requires the use of an expensive detent switch. Further, placement of the pushnuts
20
and
22
on the pushrod
14
is labor intensive and tends to be imprecise, leading to a wide variation in the minimum and maximum controlled fluid levels.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a float assembly includes a carrier rotatable about a pivot axis. The carrier includes an actuation surface which is disposed at an actuating position when the carrier is disposed at a first rotational position and which is moved away from the actuating position when the carrier is rotated away from the first rotational position toward a second rotatable position.
The float assembly may further include a pair of spaced floats coupled to the carrier. The floats may be disposed on a certain side of a vertical line extending through the pivot axis when the carrier is disposed at the first rotational position and the floats may be disposed on opposite sides of the vertical line extending through the pivot axis when the carrier is disposed at the second rotational position.
The float assembly may be used in combination with a switch having an actuation arm which is moved to a switch actuation position by the actuation surface as the carrier is rotated to the first rotational position and the actuation arm may be biased by a spring to a switch deactuation position as the carrier is rotated toward the second rotational position.
In accordance with another aspect of the present invention, a float assembly for actuating a switch based on a level of a fluid includes a pivot member having a pivot axis and a switching surface and first and second floats coupled to the pivot member. At a first fluid level, the first and second floats lie on different sides of a vertical line extending through the pivot axis and the switching surface causes the switch to assume a first switching state and, at a second fluid level, the first and second floats lie on the same side of the vertical line extending through the pivot axis and the switching surface causes the switch to assume a second switching state.
In accordance with yet another aspect of the present invention, a float assembly includes a pivot member having a pivot axis and a float coupled to the pivot member. The float provides a first torque to the pivot member in a first direction when the float lies substantially to one side of a vertical line extending through the pivot axis and a second torque in a second direction to the pivot member when the float lies substantially on another side of the vertical line extending through the pivot axis. The float assembly may further include a means for applying a third torque in the second direction to the pivot member to cause the float to move from substantially the one side to substantially the other side of the vertical line through the pivot axis.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a diagrammatic, partial sectional view illustrating a prior art configuration for a float assembly that actuates a switch based on a fluid level;
FIG. 2
is an elevational view, partially in section, of a fluid reservoir system incorporating the float assembly of the present invention with a carrier or pivot member in a first position together with a block diagram of a pump and pump motor;
FIG. 3
is a view similar to
FIG. 2
with the carrier or pivot member in a second position; and
FIG. 4
is an isometric view of the carrier or pivot member shown in FIGS.
2
and
3
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The float assembly described herein eliminates the need to use a snap-acting or detent switch and pushnuts, which are commonly used with conventional float assemblies, and instead uses one or more floats mounted on a carrier or pivot member to provide a snap-acting float assembly with hysteresis. Thus, the float assembly described herein may be used to actuate a relatively inexpensive limit switch to control the operation of a pump so that the pump motor is not subjected to rapid cycling between on and off conditions.
FIGS. 2 and 3
are views of a fluid reservoir system
50
that controls the level of a fluid between a minimum fluid level
52
and a maximum fluid level
54
. The fluid reservoir system
50
includes a container or tank
56
, a float assembly
58
, a limit switch
60
, a pump motor
62
and a pump
64
. The fluid reservoir system
50
may be, for example, a system that collects condensate (i.e., condensed water vapor) in one location and conveys the collected condensate away from the fluid reservoir system
50
.
The pump
64
is driven by the pump motor
62
and is coupled via a fluid conduit
66
to an opening
68
in the tank
56
. The pump motor
62
drives the pump
64
to remove fluid from the tank
56
via the fluid conduit
66
and conveys the removed fluid to an outlet conduit
70
, which carries the removed fluid away from the fluid reservoir system
50
. Preferably, the opening
68
is located below the minimum fluid level
52
to enable the pump
64
to draw fluid from the tank
56
when the fluid level is at or near the minimum level
52
without drawing air into the fluid conduit
66
and the pump
64
. While the pump
64
is configured to remove fluid from the tank
56
, alternative configurations may be used. For example, the pump
64
and the opening
68
may be configured so that the pump
64
adds fluid to the tank
56
via the fluid conduit
66
. Also, the pump
64
and/or motor
62
may be disposed within the tank
56
.
The pump motor
62
may be any electrical motor suitable for the particular application of the fluid reservoir system
50
. Additionally, the pump motor
62
may be integral with the pump
64
or may, alternatively, be separate from the pump
64
, in which case the pump motor
62
may be coupled to the pump
64
via a shaft, gear train, magnetic coupling, and/or any other suitable coupling mechanism.
The limit switch
60
includes a switch button
72
, a spring biased switch actuation arm
74
that is mounted to the limit switch
60
at a pivot point
76
and which may be moved against the spring bias to depress the switch button
72
, a common terminal
78
, a normally-open terminal
80
and a normally-closed terminal
82
. The common terminal
78
and the normally-open terminal
80
are serially interposed in the path of power supplied to the pump motor
62
so that when the switch button
72
is not depressed, the limit switch
60
is not activated and interrupts the flow of power to the pump motor
62
so that the pump
64
is inactive.
As is commonly known, limit switches, such as the limit switch
60
, are relatively inexpensive in comparison to snap-acting and detent switches, which are typically used with conventional float-based fluid level control systems. Although the float assembly described herein may be advantageously used within a fluid level control system (such as the fluid level control system
50
shown in
FIGS. 2 and 3
) to allow the use of an inexpensive limit switch for the control of a pump motor, conventional snap-acting and detent switches, as well as other types of switches, may nevertheless be used with the float assembly described herein.
The float assembly
58
rotates clockwise and counter-clockwise about a pivot axis
84
in response to changes in the fluid level within the tank
56
. The float assembly
58
includes a carrier or pivot member
88
, a lower float
90
disposed on centerline
92
, an upper float
94
, a switching surface
96
, and a pivot member stop surface
98
. The pivot member stop surface
98
contacts a wall
100
of the tank
56
to limit the clockwise rotation of the float assembly
58
and the upper float
94
contacts a tank stop surface
102
, which may be integral to the tank
56
, to limit counter-clockwise rotation of the float assembly
58
.
The switching surface
96
acts as a cam surface that converts the angular or rotational position of the float assembly
58
into a vertical displacement of the switch actuation arm
74
and the switch button
72
. Preferably, the switching surface
96
is profiled so that as the lower float centerline
92
moves to the right of a vertical line
104
extending through the pivot axis
84
, the switching surface
96
vertically displaces the switch actuation arm
74
to depress the switch button
72
, thereby activating the limit switch
60
. When activated, the limit switch
60
completes an electrical path between the common and normally-open terminals
78
and
80
which turns the pump motor
62
on so that fluid is removed from the tank
56
.
Generally speaking, the pivoting action of the float assembly
58
is determined by the pivot member
88
, the weight and buoyancy (which are a function of density and geometry) of the floats
90
and
94
, and the location of the floats
90
and
94
with respect to the pivot axis
84
and the vertical line
104
. As will be discussed in more detail below, the center of gravity of the pivot assembly
58
lies on or, preferably, to the right of the vertical line
104
as seen in
FIGS. 2 and 3
. Thus, when the fluid level is below the minimum level
52
, the float assembly
58
rotates to the fully clockwise position to drive the pivot member stop surface
98
against the wall
100
. While the weight and location of the floats
90
and
94
can substantially determine the center of gravity of the pivot assembly
58
, those skilled in the art will recognize that the center of gravity of the pivot assembly
58
is also determined, at least in part, by many other factors including, but not limited to, the materials and geometry of the pivot member
88
.
When the fluid level rises to contact one or more of the floats
90
and
94
, the buoyancies of the floats
90
and
94
become dominant in controlling the rotational position of the pivot assembly
58
. In general, the respective buoyant forces and torques provided by the floats
90
and
94
increase in direct proportion to the volume of fluid which is displaced by each of the floats
90
and
94
.
The magnitudes and directions of the buoyant torques exerted by the floats
90
and
94
change as the rotational position of the pivot assembly
58
varies. This is due to the fact that the direction and magnitude of the torque developed by each float are dependent upon the angle between the vertical line
104
and a line extending through the pivot axis
84
and the center of the float. Preferably (although not necessarily) the magnitude of the counter-clockwise buoyant torque provided by the upper float
94
increases as the pivot member
88
rotates counter-clockwise from the fully clockwise position to the fully counter-clockwise position. On the other hand, the magnitude of the torque provided by the lower float
90
decreases to zero as the pivot member
84
rotates to bring the lower float centerline
92
into coincidence with the vertical line
104
and increases from zero as the lower float centerline
92
moves to the right of the vertical line
104
.
One particularly interesting aspect of the float assembly
58
is that the direction of the buoyant torque provided by the lower float
90
changes abruptly as the lower float centerline
92
crosses the vertical line
104
. Specifically, when the lower float centerline
92
lies to the left of the vertical line
104
, the lower float
90
provides a clockwise buoyant torque and when the lower float centerline
92
lies to the right of the vertical line
104
, the lower float
90
provides a counter-clockwise buoyant torque. As described in more detail below, this abrupt reversal in the direction of the buoyant torque provided by the lower float
90
results in a snap-action pivoting movement for the pivot assembly
58
.
The manner in which the above-described torques interact to provide a snap-acting float assembly with hysteresis can be best understood in connection with the following exemplary description of the operation of the fluid reservoir system
50
of
FIGS. 2 and 3
. Initially, the tank
56
is empty, and because the center of gravity of the pivot assembly
58
lies to the right of the vertical line
104
, the pivot member
58
to rotates fully clockwise to drive the pivot stop surface
98
against the wall
100
. With the float assembly
58
in the fully clockwise position (i.e., with the pivot member stop surface
98
in contact with the wall
100
), the switching surface
96
is spaced from the switch actuation arm
74
allowing the arm
74
to be biased downwardly so that the switch button
72
is not depressed. As a result, the pump motor
62
and pump
64
are off, and fluid is not removed from the tank
56
.
As the fluid level within the tank
56
rises, the fluid first contacts the lower float
90
, which causes the lower float
90
to exert a clockwise buoyant torque on the float assembly
58
, thereby holding the pivot member stop surface
98
firmly in place against the wall
100
(as shown in FIG.
2
). Further, as the fluid level continues to rise, an increasing proportion of the lower float
90
becomes submerged which increases the clockwise buoyant torque provided by the lower float
90
. When the fluid level rises sufficiently high to completely submerge the lower float
90
, the lower float
90
exerts a maximum clockwise buoyant torque on the pivot assembly
58
.
When the fluid level rises to contact the upper float
94
, the upper float
94
begins to provide a counter-clockwise buoyant torque to the pivot assembly
58
. Eventually, when a sufficient portion of the upper float
94
becomes submerged, the counter-clockwise buoyant torque provided by the upper float
94
exceeds the maximum clockwise buoyant torque provided by the lower float
90
. This effect may be achieved in any suitable manner, such as by designing the upper float
94
to have a greater buoyancy than the lower float
90
and/or locating the upper float
94
at a suitable distance from the pivot axis
84
relative to the distance of the lower float
90
from the pivot axis
84
, etc. In any event, further increases in the fluid level cause the pivot assembly
58
to rotate counter-clockwise. When the fluid level rises sufficiently (i.e., to the maximum fluid level
54
) to cause the lower float centerline
92
to cross the vertical line
104
, the clockwise buoyant torque provided by the lower float
90
abruptly changes direction to become a counter-clockwise buoyant torque which, without any further increase in the fluid level, causes the float assembly
58
to rotate fully counter-clockwise so that the upper float
94
is driven against the tank stop surface
102
(as shown in FIG.
3
). Additionally, as the lower float centerline
92
crosses to the right of the vertical line
104
, the switching surface
96
displaces the switch actuation arm
74
upward to depress the switch button
72
and activate the limit switch
60
. When activated, the limit switch
60
provides an electrical path between the common and normally-open terminals
78
and
80
to turn the pump motor
62
on, which drives the pump
64
to remove fluid from the tank
56
.
As the pump
64
decreases the fluid level within the tank
56
to below the level of the upper float
94
, the float assembly
58
remains rotated fully counter-clockwise with the upper float
94
driven against the tank stop surface
102
. The float assembly remains in the fully counter-clockwise position because the lower float centerline
92
remains to the right of the vertical line
104
and the lower float
90
provides a counter-clockwise buoyant torque that is greater than the clockwise torque provided by the weight of the pivot assembly
58
. As a result, the limit switch
60
continues to provide power to the pump motor
62
and the pump
64
continues to remove fluid from the tank
56
.
When the fluid level decreases to about the minimum level
52
(as shown in FIG.
2
), the counter-clockwise buoyant torque provided by the lower float
90
becomes substantially zero and the clockwise torque provided by the weight of the pivot assembly
58
causes the float assembly
58
to rotate fully clockwise to drive the pivot member stop surface
98
against the wall
100
, thereby allowing the spring biased switch actuation arm
74
to move downward to deactivate the limit switch
60
, which turns off the pump motor
62
so that the pump
64
stops removing fluid from the tank
56
.
As can be understood from the above discussion of the operation of the float assembly
58
, the switching surface
96
of the float assembly
58
causes the limit switch
60
to switch between two switching states so that one of the two states turns the pump motor
62
on at the maximum fluid level
54
and the other of the two switching states turns the pump motor
62
off at the minimum fluid level
52
. Thus, the operation of the float assembly
58
provides switching hysteresis that eliminates rapid cycling of the pump motor
62
. Additionally, the float assembly described herein provides a positive detent or snap-action switching action due to the reversal of the direction of the buoyant torque provided by lower float
90
that occurs as the lower float centerline
92
crosses the vertical line
104
.
Those skilled in the art will recognize that the floats
90
and
94
may be made from any suitable material providing buoyancy such as, for example, styrofoam. Additionally, the floats
90
and
94
may be approximately spherical in shape or may, alternatively, be of any other shape needed to accomplish the above-described pivoting action in response to a fluid level. In fact, the floats
90
and
94
may be integrated so that the function of the separate floats
90
and
94
is accomplished using a substantially one-piece float. Further, the shape, material, volume, location with respect to the pivot axis
84
and one another, etc. of the floats
90
and
94
may be different, if needed, to provide any desired pivoting action, minimum fluid level, maximum fluid level, etc. Still further, those skilled in the art will recognize that the upper float
94
may be eliminated altogether and instead a lever arm or any other mechanical and/or electromechanical device may be substituted and manually or automatically controlled based on fluid level or some other parameter to apply a torque to the pivot assembly
58
to cause the lower float centerline
92
to cross the vertical line
104
.
FIG. 4
is an exemplary isometric view of a pivot member
120
that may be used with the float assembly
58
shown in
FIGS. 2 and 3
. The pivot member
120
includes barbed fittings
122
and
124
for securely engaging with complementary openings (not shown) in the floats
90
and
94
, shoulder portions
126
and
128
, a pivot bearing
130
, a cam surface
132
, and stops
134
and
136
. Fillets or webs
138
and
140
(and other fillets which are not shown) may be included to strengthen the shoulder portions
126
and
128
to prevent breakage of the barbed fittings
122
and
124
when pressing the floats
90
and
94
onto the barbed fittings
122
and
124
. Preferably, the pivot member
120
is a one-piece structure molded from a thermoplastic material. Alternatively, the pivot member
120
may be a die-cast part or may be fabricated using one or more component pieces from plastics, metals, and/or any other suitable materials.
Those of ordinary skill in the art will readily appreciate that a range of changes and modifications can be made to the preferred embodiments described above. The foregoing detailed description should be regarded as illustrative rather than limiting and the following claims, including all equivalents, are intended to define the scope of the invention.
Claims
- 1. A float assembly, comprising:a carrier rotatable about a pivot axis and including an actuation surface which is disposed at an actuating position when the carrier is disposed at a first rotational position and which is moved away from the actuating position when the carrier is rotated away from the first rotational position toward a second rotatable position; and a pair of spaced floats coupled to the carrier wherein the floats are disposed on a certain side of a vertical line extending through the pivot axis when the carrier is disposed at the first rotational position and wherein the floats are disposed on opposite sides of the vertical line extending through the pivot axis when the carrier is disposed at the second rotational position.
- 2. The float assembly of claim 1, in combination with a switch.
- 3. The float assembly of claim 2, wherein the switch includes an actuation arm which is moved to a switch actuation position by the actuation surface as the carrier is rotated toward the first rotational position.
- 4. The float assembly of claim 2, wherein the actuation arm is biased by a spring to a switch deactuation position as the carrier is rotated toward the second rotational position.
- 5. The float assembly of claim 1, in combination with a container within which the float assembly is mounted.
- 6. The float assembly of claim 5, wherein the container includes a container stop surface which is contacted by one of the floats when the carrier is disposed in the first rotational position.
- 7. The float assembly of claim 5, wherein the carrier includes a carrier stop surface that contacts a wall of the container when the carrier is disposed in the second rotational position.
- 8. The float assembly of claim 5, wherein the container is adapted to hold a liquid having a varying liquid level and wherein one of the floats is disposed below the other float and the one float exerts a torque in a first direction on the carrier when the liquid level is above a first level but below a second level and exerts a torque in a second direction different than the first direction on the carrier when the liquid level is above the second level.
- 9. The float assembly of claim 8, wherein the other float exerts a torque in the second direction when the liquid level is above the second level.
- 10. The float assembly of claim 1, wherein a center of gravity of the carrier and the floats is disposed on the certain side of the vertical line extending through the pivot axis.
- 11. A float assembly for actuating a switch based on a level of a fluid, the float assembly comprising.a pivot member having a pivot axis and a switching surface; a first float coupled to the pivot member; and a second float coupled to the pivot member, wherein at a first fluid level the first and second floats lie on different sides of a vertical line extending through the pivot axis and the switching surface causes the switch to assume a first switching state, and wherein at a second fluid level the first and second floats lie on the same side of the vertical line extending through the pivot axis and the switching surface causes the switch to assume a second switching state.
- 12. The float assembly of claim 11, wherein the first float is coupled to the pivot member at a first location with respect to the pivot axis and the second float is coupled to the pivot member at a second location with respect to the pivot axis.
- 13. The float assembly of claim 11, wherein the first float provides a first buoyant torque about the pivot axis and the second float provides a second buoyant torque about the pivot axis greater than the first buoyant torque.
- 14. The float assembly of claim 13, wherein the first and second buoyant torques are in different directions.
- 15. The float assembly of claim 11, wherein the switching surface comprises a cam surface that is profiled to actuate the switch between on and off states when a centerline of one of the first and second floats crosses the vertical line extending through the pivot axis.
- 16. The float assembly of claim 11, further including a pump coupled to the switch and wherein the first switching state turns the pump off to allow the fluid level to increase and the second switching state turns the pump on to cause the fluid level to decrease.
- 17. The float assembly of claim 11, wherein the first and second floats have substantially the same shape.
- 18. The float assembly of claim 11, wherein the first and second floats have substantially the same density.
- 19. A float assembly, comprising:a pivot member having a pivot axis; a float coupled to the pivot member to provide a first torque to the pivot member in a first direction when the float lies substantially to one side of a vertical line extending through the pivot axis and a second torque in a second direction to the pivot member when the float lies substantially on another side of the vertical line extending through the pivot axis; and means for applying a third torque in the second direction to the pivot member to cause the float to move from substantially one side to substantially the other side of the vertical line through the pivot axis.
- 20. The float assembly of claim 19, wherein the means for applying the third torque comprises a second float.
- 21. The float assembly of claim 20, wherein at a first level of a fluid the first and second floats lie on different sides of the vertical line extending through the pivot axis and wherein at a second level of the first and second floats to lie on the same side of the vertical line extending through the pivot axis.
- 22. The float assembly of claim 19, wherein the pivot member further includes a switching surface that causes a switch to switch between first and second switching states associated with respective first and second levels of a fluid.
- 23. A float assembly for use in controlling a fluid within a fluid reservoir system having a tank that holds the fluid, a pump motor, and a limit switch serially interposed in an electrical path supplying power to the pump motor, the float assembly comprising:pivot member having a pivot axis and a switching surface; a first float coupled to the pivot member; and a second float coupled to the pivot member, wherein at a first level of the fluid in the tank the first and second floats lie on different sides of a vertical line extending through the pivot axis and the switching surface causes the limit switch to assume a first switching state that changes the flow of power to the pump motor, and wherein at a second level of the fluid the first and second floats lie on the same side of the vertical line extending through the pivot axis and the switching surface causes the limit switch to assume a second switching state that changes the flow of power to the pump motor.
- 24. The float assembly of claim 23, wherein the first float provides a first buoyant torque about the pivot axis which is less than a second buoyant torque provided by the second float.
- 25. The float assembly of claim 24, wherein the first and second buoyant torques oppose one another.
- 26. The float assembly of claim 23, wherein the second fluid level is greater than the first fluid level.
- 27. The float assembly of claim 23, wherein the first switching state turns the pump motor off and the second switching state turns the pump motor on.
- 28. The float assembly of claim 23, wherein the first switching state allows the fluid level in the tank to increase and the second switching state allows the fluid level in the tank to decrease.
- 29. The float assembly of claim 23, wherein the first and second floats have substantially the same shape.
- 30. The float assembly of claim 23, wherein the first and second floats have substantially the same volume.
- 31. The float assembly of claim 23, wherein the first and second floats have substantially the same density.
US Referenced Citations (22)