Fluid level activated float switch

A fluid level responsive switch apparatus used in a tank to monitor fluid level in the tank. The apparatus has a float buoy attached to a tilt switch containing three conductors activated by a conductive sphere. The first conductor activates the fluid controller for restoring fluid to the tank when the conductive sphere is in a low fluid level position, the second conductor delays the switching between the activating and deactivating conductors when the conductive sphere is in an intermediate level position and the third conductor deactivates the controller when the conductive sphere is in a high fluid level position.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to a fluid level activated electrical switch 
and more particularly to a float switch for use in conjunction with a 
controller to automatically restore or drain fluid to a desired level by 
supplying power to a pump motor or a solenoid operated valve. 
Switches responsive to fluid levels have utilized a variety of approaches 
for opening and closing an electrical circuit. Fluid level switch devices 
usually incorporate a float buoy for sensing the fluid level, the float 
buoy being operatively connected to a switch device. Mercury switches 
provide excellent switching characteristics and are readily adaptable to 
fluid level actuated float switches. They usually consist of a sealed 
glass tube of mercury into which a pair of electrodes extend. When tipped 
at a predetermined angle, the mercury will travel through the tube to 
bridge a gap between the two electrodes to actuate the switch. However, 
mercury is a hazardous material and there has been movement away from its 
use in float switches, especially where breakage of the glass tube is 
possible. 
One alternative to a mercury-switch based float switch has been to replace 
the mercury tube with an enclosed raceway containing a conductive sphere. 
The sphere travels through the raceway as the float buoy moving up and 
down according to the fluid level tips the switch member. The sphere will 
contact an arm or yoke which will activate or deactivate the load, as 
disclosed in U.S. Pat. No. 5,087,801 to Johnston, U.S. Pat. No. 3,944,770 
to Pepper, U.S. Pat. No. 4,592,576 to Frede, U.S. Pat. No. 4,644,117 to 
Grimes her conductive spheres contact conductive strips etched onto the 
raceway such as disclosed in U.S. Pat. No. 3,733,447 to Schneider, Jr. 
A problem arises when the fluid levels monitored do not change uniformly. 
Wave action, for example, may cause prior art devices to switch on and off 
frequently and erratically causing burn out of the attached motors. 
Therefore, what is needed is a fluid level responsive electrical float 
switch which does not subject the motor to erratic energization, a cause 
of burnout The present invention solves this problem by providing a 
conductive ball to make a direct contact with conductive switch contacts 
in three different positions, one of which is a neutral, intermediate 
position, within a fluid level activated float switch. The neutral 
intermediate position of the present invention operates as a delay 
mechanism which prevents wave action in the fluid from turning on and off 
the load. 
SUMMARY OF THE INVENTION 
The present invention is a fluid level responsive float switch consisting 
of a tilt switch attached to the arm of a hinged float buoy. The tilt 
switch includes wire contact elements spanning the interior of a casing 
and a conductive ball held in position by the contact wire elements The 
float buoy rises and falls with the level of the fluid being regulated. 
When the fluid being regulated is high, the float buoy is in a position 
such that the tilt switch on the arm of the hinged float is tilted back 
towards the hinge. The conductive ball is held in position by the contact 
elements of a first and second conductor. When the float is in the neutral 
intermediate position, the ball repositions and is held by the contact 
elements of only the second conductor. When the fluid being regulated is 
low the float buoy is in a third position, the plastic case tilts downward 
away from the hinge and the ball repositions to be held by the contact 
elements of both the second and third conductor. 
The activation or deactivation of the load results from the position of the 
conductive ball in the tilt switch. To accomplish switching of a power 
relay for the activating or deactivating of the load, two six volt control 
relays are utilized. The first control relay is a single pole, single 
throw, normally closed relay and the second control relay is a double 
pole, single throw, normally opened relay. When the float switch is in one 
position, such as when the fluid being monitored is low, the ball is held 
in position by bridging the contact elements of the second and third 
conductors. This causes one pole of the normally open, second control 
relay to close. When the second control relay closes, the power relay is 
activated and power is supplied to the load. The other pole completes a 
circuit parallel to the conductive ball. As the float position changes 
with the fluid level and the ball repositions to its neutral position 
contacting only the second conductor. In the neutral position, a delay is 
imposed and the load remains on because of the latching action of the pole 
that is in parallel with the ball. Likewise, the neutral position also 
imposes a delay when switching from off to on as the fluid level drops. 
When the fluid level is high, the ball repositions within its housing to 
bridge the contacts of the first conductor and the neutral conductor. This 
will temporarily open the normally closed relay and break the latching 
circuit holding the second control relay closed. When the second control 
relay returns to its open position and the power relay disengages, 
stopping the flow of power to the load. 
In an alternative circuitry arrangement a single throw, three pole normally 
open relay replaces the power relay and the two control relays. When the 
relay is energized, the load to the pump is on. When the relay is 
de-energized, the load to the pump is off. The circuit shunts the relay 
coil when the fluid level is high to disconnect the power to the load. In 
another alternative circuitry arrangement, a two coil latching relay can 
be used to replace the power relay and two control relays. Power is 
supplied to the pump when the latching relay is energized to close its 
poles. Power is cut off to the pump when the latching relay is energized 
and the poles open. 
OBJECTS 
The primary object of the present invention is to provide a reliable and 
accurate fluid level responsive float switch which is highly resistant to 
turning on and off due to wave action thereby protecting any connected 
motor from burn out. 
Another object of the invention is to provide a fluid level actuated float 
switch which does not use hazardous material such as mercury. 
Yet another object is to provide a fluid level activated float switch which 
operates at a low voltage near the fluid and tanks so that people or 
animals are not in danger from accidental electrocution. 
Still another object is to provide a fluid level activated switch having 
more versatility. 
These and other objects of the present invention will become apparent to 
those skilled in the art upon a study of the following specification, 
pending claims and accompany drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is a float switch responsive to fluid level changes. 
As shown in FIG. 1 the invention, designated generally by numeral 5, has a 
control box 10, and arm member 12, a tilt switch 14, a float buoy 16 and 
electrical connecting leads 18 and 20. Float buoy 16 and tilt switch 14 
are located in the tank 2 whose fluid level is being controlled. 
The tilt switch 14 is located on an hinge arm 12. Hinge arm 12 is pivotally 
hinged at 24 and connected to a support member 26. Support member 26 is 
ideally an elongated bar for securing the float buoy 16 and tilt switch 14 
to the edge of tank 2 being regulated. As shown in FIG. 1, hinge arm 12 
has a bent end 28 to allow the required tilt angle for operation of the 
present invention. Buoy stem 23, attached to the base of hinge arm 12 by U 
bolt 15, extends through opening 29 on the bent end 28 after hinge arm so 
as to inhibit lateral sway of the float buoy 16. Float buoy 16 a 
conventional toilet ball or, alternatively a piece of buoyant foam. The 
float rod 23 is designed to telescope into float buoy to provide 
adjustment of the rod length. By adjusting the position of the float buoy 
16 on the float rod, the fluid level drop between the "on" and "off" 
cycles can be varied. 
Tilt switch 14 as shown in FIGS. 4A-4C has a plastic case 30 totally 
enclosing a metal conductive ball 32 and three wire conductors designated 
34, 36 and 38. The case is a generally rectangular closed box with side 
walls 25 and 27, end walls 37 and 31, base 33 and top 35 as shown in FIG. 
2 and 4A-C. The conductors 34, 36 and 38 extend through the wall 27 of the 
case, as shown in FIG. 3 and serve as contact elements within the case 30 
for supporting the conductive ball 32 in the manner to be described. 
Contact elements 40 and 42 tied to the second conductor 36 are located in 
the lower portion of case 30 and spaced apart parallel relationship as 
shown in FIG. 4. Contact element 44 connected to the first conductor 34 
and contact element 46 connected to the third conductor 38 are located on 
opposing sides of contact elements 40 and 42 and are vertically displaced 
to reside in the upper portion of case 30. These contacts are spaced to 
hold ball 32 in three discrete positions as the case is tipped from the 
horizontal in the clockwise or counterclockwise direction. In the high 
fluid level position ball 32 bridges contact elements 40 and 44 as shown 
in FIG. 4A. In the intermediate fluid level position ball 32 bridges 
contact elements 40 and 42 as shown in FIG. 4B. In the low fluid level 
position ball 32 bridges contact elements 42 and 46 as shown in FIG. 4C. 
Turning now to FIG. 5, the circuitry contained within the control box 10 of 
FIG. 1 will now be explained. The control circuit includes a first control 
relay 50 having a relay coil 51 which, when energized, functions to open 
the normally closed contacts 51(a) and 51(b). A second control relay 52 
has a relay coil 53 which, when energized, functions to close the normally 
open contact pair 53(a) and 53(b) as well as the contact pair 53(c) and 
53(d). Also included is a power relay 54 having a relay coil 55. The 
contacts 55(a) and 55(b) and the contacts 55(c) and 55(d) are normally 
open but become closed when the coil 55 is energized. 
A terminal strip 56 includes a plurality of tie points 58, 60, 62, 64, 66 
and 68 which are adapted to be connected by jumper links to a 
corresponding plurality of tie points 70, 72, 74, 76, 78 and 80. The 
conductors 82 and 84 are adapted to be connected to a source of line 
voltage, such as a 220 volt supply or 120 volt supply, such that 110 volts 
exists between tie point 60 which is connected to ground. A primary 
winding 86 of a voltage step-down transformer is connected across the tie 
points 70 and 72 and, thus, the primary voltage will be 120 volts. The 
secondary winding 88 of the step-down transformer 85 may develop six volts 
across it. 
Conductor 38, leading to contact 46 of the tilt switch, connects to one 
side of the secondary winding 88 of the step-down transformer 85 by way of 
a conductor 90 and it also is connected by a conductor 92 to the contact 
51(a). The other side of the secondary winding 88 is connected by a 
conductor 94 and a conductor 96 to one side of the relay coil 51. It is 
also connected by the conductor 94 and a further conductor 98 to a first 
side of the relay coil 53. The second side of the relay coil 51 is 
connected by a conductor 100 to the conductor 34 which, as mentioned, 
joins to the contact 44 in the tilt switch. The remaining terminal of the 
relay coil 53 is connected by a conductor 102 to a junction point 104 to 
which the conductor 36 joins. Conductor 36 leads to the contacts 40 and 42 
of the tilt switch. 
Conductor 36 also is joined to the relay contact 53(d) by way of conductor 
106 and its mating contact, 53(c), is connected by a conductor 108 to the 
normally closed contact 51(b). With continued reference to FIG. 5, the tie 
point 70 on the junction strip 56 is connected by a conductor 110 to a 
junction 112 to which the normally open contact 53(b) connects, via 
conductor 114. The contact 53(a) is joined by conductors 116 and 118 to 
the relay coil 55. The other terminal of the coil 55 is coupled by a 
conductor 120 to grounded terminal point 78. 
The load to be controlled is adapted to be connected across the lines 122 
and 124. The load may, for example, be a pump for introducing additional 
water into the tank. The load terminal 122 is connected via terminal strip 
56 and a conductor 126 to the contact 55(a) while the line 124 is 
connected via the terminal strip and a conductor 128 to the contact 55(c). 
Contact 55(b) is joined by a conductor 130 to one side of the AC line 
while the other AC line 82 is joined via terminal strip contacts 58-70 and 
a conductor 132 to the contact 55(d). 
Turning now to FIG. 6, a first alternative embodiment of the circuitry 
control is shown. The control circuit includes a three pole, single throw 
normally open relay 210 having a relay coil 215. This relay replaces the 
power relay and the two control relays of the first embodiment When 
energized, relay coil 215 functions to close normally open contact pair 
214(a) and 214(b) as well as contact pair 216(a) and 216(b). The control 
circuits also include a current limiting resistor 222 disposed between the 
relay 210 and the tilt box 200. Conductors 223a and 223b lead to the 
pump's power source. Conductors 225a and 225b lead to the pump motor. 
The primary winding 225 of voltage step down transformer 227 is connected 
to 120 volts. The secondary winding 230 may develop 6 volts across. 
Conductor 232 leading to the contact 46 of tilt switch 200 connects to one 
side of the secondary winding 230 of the step down transformer 227 by way 
of conductor 234 which in turn is connected to conductor 232 at junction 
point 233. Current limit resistor 222 is connected to junction point 233 
by conductor 238 and contact 46 by conductor 232. Conductor 231 leads from 
current limiting resistor 222 to mating contact 239(a). 
The other side of the secondary winding 230 is connected by conductor 240 
to junction point 242. Conductor 246 leads from junction point 242 to 
contact 44. Conductor 244 leads from junction point 242 to relay coil 215 
and conductor 245 leads from the relay coil 215 to junction point 250. 
Contact elements 42 and 40 are connected to the relay coil 215 through 
conductor 248 by way of junction point 250 and conductor 245. Contact 
elements 42 and 40 are also connected to mating contact 239(b) through 
conductor 248, junction point 250 and conductor 249. 
Turning now to FIG. 7, another alternative control circuit is disclosed. In 
this circuit arrangement, the two relays of the preferred embodiment are 
replaced with a two coil latching relay 308. This relay 308 requires D.C. 
Adaptor, designated generally as 310, to change in 120V AC to 12 V DC. 
Contact 44 of tilt switch 300 is in series with coil 312 of latching relay 
308 via conductor 309 and contact 46 of tilt switch 300 is in series with 
coil 314 of latching relay 308 via conductor 311. When coil 314 is 
energized, the contact pair 316(a) and 316(b) close as do contact pair 
318(a) and 318(b). When coil 312 is energized, the contact pairs open. 
Conductors 320 and 322 lead from the power source for the pump being 
regulated to contact elements 316(a) and 318(b) respectively. Conductors 
324 and 326 lead to the pump motor. Conductor 328 is located between coil 
312 and junction point 330. Conductor 332 is located between coil 314 and 
junction point 330. Between junction point 330 and DC adaptor 310 is 
conductor 334. The DC adaptor is also connected to a power source (not 
shown) which will provide 120 V AC. Conductor 336 leads from DC Adaptor 
310 to junction point 338 from which contacts 40 and 42 of tilt switch 300 
are joined. 
MODE OF OPERATION 
The device is operatively positioned to monitor fluid level such as 
fastening it to the edge of the tank 2 as shown in FIG. 1, or to a post 
anchored with a submerged weight in the interior of the tank such as shown 
in FIG. 4A-4C. The float buoy 16 will rise and fall with the level of the 
fluid being regulated as shown by FIGS. 4A-4C. The position of the tilt 
switch and buoy 16 shown in FIG. 4C is the proper position for the device 
5 when the tank 2 is empty. The control pump must be activated to fill the 
tank 2. The tilt switch 14 and arm 12 is tilted away from the support 
member 26. The conductive ball 32 is positioned to bridge the contact 
elements 42 and 46 of conductors 36 and 38. 
With the conductive ball bridging the contacts 42 and 46 and with the 110 
voltage applied across the supply lines 82 and ground 83, a current will 
flow from one side of the secondary winding 88 of the transformer 85 and 
through conductors 94 and 98 and thence through the relay winding 53 and 
conductor 102, the conductive ball and the conductor 90 back to the other 
side of the secondary winding. Thus, relay coil 53 will be energized 
causing relay contacts 53(a)-53(b) to close and 53(c) and 53(d) to also 
close. When contacts 53(a) and 53(b) mate, a current path is established 
the AC supply line 82 through conductor 110, conductor 114, the now-closed 
contacts 53(a)-53(b), conductor 116 and conductor 118 to the relay coil 55 
whose other terminal is connected by a conductor 120 to ground. Hence, the 
relay coil 55 will be energized such that contact 55(a) mates with contact 
55(b) and contact 55(c) mates with contact 55(d). At this time, relay coil 
51 remains unenergized and contacts 51(a) and 51(b) remain closed. 
It is immediately apparent from the schematic diagram of FIG. 5 that when 
the relay 55 is energized, the 220 volt AC supply becomes connected across 
the load lines 122 and 124 leading to the pump. Hence, the pump will be 
energized and will begin introducing water into the tank. As the water 
continues to flow into the tank, the float buoy will rise. A point will be 
reached when the ball 32 will assume the intermediate position shown in 
FIG. 4B bridging contacts 40 and 42, each of which are tied to the 
conductor 36. However, since contacts 53(c) and 53(d) of relay 53 have 
previously been closed, relay 53 still remains energized via the current 
from the secondary winding 88 flowing through path including conductor 94, 
conductor 98, coil 53, conductor 102, conductor 106, contacts 53(c) and 
53(d), conductor 108, contacts 51(a) and 51(b), the conductor 92 and 
conductor 90 back to the other side of the secondary winding. Thus, even 
though the ball is shifted to the intermediate fluid level position, the 
pump remains energized through the contacts of the power relay 55. 
Finally, when the water level reaches the point where the ball in the float 
switch 14 moves to the high fluid level position shown in FIG. 4A so as to 
bridge the contacts 40 and 44, the current will now flow from the 
secondary winding 88 of the step-down transformer, via conductors 94 and 
96 through the relay coil 51 and then via conductor 100 and the conductive 
ball to conductor 36 and thence through conductor 106, contacts 53(d) and 
53(c), then via conductor 108 to 51(b) and 51(a) back to the other side of 
the step-down transformer secondary winding 88. As such, both relay coils 
51 and 53 will be energized. Once relay coil 51 energizes, its contacts 
51(a) and 51(b) break interrupting the current flow through the relay coil 
53, causing contacts 53(a) and 53(b) to break and contacts 53(c) and 53(d) 
to also break. When this happens, of course, the current path for the 
relay coil 55 is interrupted causing its contacts 55(a)-55(b) and 
55(c)-55(d) to break, disconnecting the AC supply from the load. Thus, the 
pump will stop at this point. The circuit will remain open when wave 
action causes the conductive, ball 32 to be repositioned between the high 
level position and intermediate fluid level position. 
The conductive ball 32 does not alter positions just between the contacts 
for activating and deactivating first and third conductors. Instead, the 
ball 32 contacts an intermediate pair of contact elements 40 and 42. 
Contacts 53c-53d of the second control relay 52 is in parallel arrangement 
with the ball 32 when the controller is on and the ball is in the high 
fluid level position shown in FIG. 4C. This same contact pair is in series 
with the conductive sphere 32 when the controller is off and ball 32 is in 
the high fluid level position shown in FIG. 4A. The ball 32 is in series 
with the voltage source when in the high fluid level and the low fluid 
level positions. Float switch contacts 40-42 merely delays the switching. 
Thus, as the tank 2 is filling and the tilt switch 14 is pivoted 
counterclockwise, the ball 32 rolls from the low fluid level position to 
the intermediate fluid level position. The load will remain on although 
the ball 32 has released its contact from the low fluid level position. 
The load cannot be deactivated until the ball 32 repositions itself into 
high fluid level position. Likewise, as the tank 2 is draining and the 
tilt switch 14 is pivoted clockwise, the ball 32 repositions itself from 
between the first conductor 34 location, which deactivated the pump to the 
intermediate conductor 36. The controller cannot be activated until the 
conductive ball 32 repositions itself between the contact elements 42 and 
46 of the second and in the low fluid level position. 
The intermediate fluid level position is an advantage because the fluid 
level when rising or falling is not smooth. The fluid responsive switches 
responds to wave action. The intermediate fluid level position will 
prevent the sphere from repositioning between the contact elements 
activating and deactivating the pump because of wave action. This avoids 
continual activation and deactivation which will burn out the pump motor. 
The apparatus is therefore highly resistant to turning on and off due to 
wave action. 
The ball 32 in the tilt switch 14 may remain in the off position for an 
extended period of time. The six volt source of energy for the activating 
first control relay 50 to the open position is in series with contacts 
53(c) and 53(d) of the second control relay 52 and thus also becomes 
deactivated. Thus, the first control relay 50 opens and closes again to 
the rest position quickly. 
The first alternative embodiment of the circuitry control shown in FIG. 6 
operates as follows. As the metal ball in the tilt switch makes contact 
between elements 42 and 46, it completes the circuit of the secondary 230 
of the step down transformer 227. The relay 210 closes since the coil 215 
of the relay 210 is in series in this circuit. The pole of the relay 210 
containing contact 239(a) and 239(b) is in parallel to the metal ball 270 
and holds the completed circuit through the relay coil 215 as the metal 
ball 270 repositions itself when the fluid level rises. 
When the fluid level rises to the point where the metal ball 270 
repositions to contact elements 40 and 44 of the tilt switch, it completes 
a circuit which shunts the coil 215 of the relay 210. This shunt has a 
much lower resistance than the relay coil 215, so the current flow 
bypasses the coil 215 and there is no difference of potential across the 
coil 215. This causes the contacts in relay 210 to open, disconnecting the 
power to the load. It also opens the circuit of the transformer secondary 
230 so there is no further current flow through the tilt switch 200. The 
current limiting resistor 222 is employed in this system to prevent a 
"dead short" of the transformer secondary 230 when the relay coil 215 is 
shunted by the metal ball 270 when it contacts elements 40 and 44 of the 
tilt switch. 
The full voltage of the transformer secondary is employed across the relay 
coil when the metal ball contacts elements 42 and 46 of the tilt switch to 
activate the relay. When the metal ball 270 repositions to cease contact 
between elements 42 and 46 of the tilt switch, less than the full 
transformer secondary voltage drop occurs across the relay coil 215 
because there is some voltage drop across the current limiting resistor 
222 in series with the coil 215. This does not adversely affect the 
operation of the relay because less electro-magnetic force is required to 
hold the contact than is required to draw them closed from a gapped 
position. 
In the alternative circuit arrangement disclosed in FIG. 7, the circuit 
operation will now be described. When the ball 321 bridges contacts 42 and 
46, a circuit is completed through the DC adaptor 310, the metal ball 321, 
and relay 308. This energizes the coil 314 and contact pairs 316(a) and 
316(b) close as do contact pair 318(a) and 318(b). The closing of the 
contact pairs completes the circuit between the load source and pump, and 
water is supplied to the tank. As the tank fills and the tilt box 300 
moves, the ball 321 repositions to bridge contacts 40 and 42. The coil 314 
is energized but the load remains on because the latching contact pairs 
316(a) and 316(b) and 318(a) and 318(b) remain closed. Once the tank is 
full, the ball 321 has repositioned to bridge contacts 44 and 40. This 
completes the circuit through the ball 321 and the DC adaptor 310 to 
energize coil 312 and opens the closed contact pairs 316(a) and 316(b) and 
318(a) and 318(b). The circuit between the load and the pump breaks and 
water is no longer supplied to the tank. 
The three position tilt switch 14 or 200 as designated in the first 
alternative embodiment is used so that more versatility is available, 
although other position tilt switch will work. A certain number of degrees 
tilt, such as 25 degrees, is required to reposition the ball. A wider or 
narrower range of fluid level for each cycle can be chosen by changing the 
tilt switch Thus a shorter float buoy stem can be used with the three 
position tilt switch to respond to smaller fluid fluctuations than float 
buoys with longer stems 
Alternative arrangements in the tilt switch are shown in FIGS. 8A-8C. The 
four position tilt switch of 8A is useful if a greater degree of tilt is 
desired to reposition the ball 134 from the start to stop position. This 
arrangement has a similar arrangement of contact elements for the three 
conductors, however, it adds one wire between the intermediate contact 
elements Contact element 135 is connected to the first conductor of the 
circuit contact elements 136 and 137 are connected to the intermediate 
conductor of the circuit arrangement and contact element 138 is connected 
to the third conductor of the circuit arrangement. Wire 139 spans the 
interior of the case but is not operatively connected to the circuit 
arrangement. A two position tilt switch is shown in FIG. 8B. In this 
arrangement there is only one contact element 144 connected to the 
intermediate conductor of the circuit arrangement. Contact element 145 is 
connected to the first conductor of the circuit arrangement and contact 
element 146 is connected to the third conductor of the circuit 
arrangement. Although this tilt switch requires a lower degree of tilt 
between the on and off positions, the telescoping float rod can be 
adjusted to compensate for the smaller degree of tilt required with this 
two position tilt switch. 
In FIG. 8C contact element 148 is connected to the first conductor of the 
circuitry. Contact element 149 is connected to the intermediate conductor 
of the circuit arrangement and contact element 150 is connected to the 
third conductor of the circuit arrangement. Lastly, contact element 151 is 
connected to the intermediate conductor. This arrangement cuts the fluid 
level fluctuation range by about 50%. If the power turns off while the 
ball bridges 149 and 150 and the fluid level drops repositioning the ball 
between 150 and 151, the switch will still turn on when power is restored. 
This invention has been described with a certain degree of particularity, 
it is to be understood that the present disclosure has been made only by 
way of example and that numerous changes in details of construction in 
arrangement of parts may be resorted to, such as reversing the first and 
third conductor leads to the tilt switch for automatically lowering the 
fluid level as in a sump, without departing from the true spirit and scope 
of the invention.