FIELD OF THE INVENTION
The present inventions relates to a float switch and, in particular, to a liquid level control
float switch system specifically useful to start and stop pumps used for the purpose of
dewatertng the sump pits and filling of overhead tanks and other similar applications.
The liquid level control float switch system is simple to obtain, safe and free of
environmental hazards, user friendly and also cost effective as compared to conventional
float switches presently available.
BACKGROUND ART
Generally float switches are provided to automatically start and stop the dewatering
pumps used in industry and home applications. All these are used for overhead water
tanks pumps. In industry, these are used for dewatering of sump pits in various cellars,
cable galleries where water accumulation occurs due to leakage water and underground
seepage water. In such cases, dewatering pumps are installed to work in automatic
mode. Without any manual intervention, these pumps start automatically when the
water level exceeds a predetermined level and stops when level goes down below a
particular level.
The most common type of float switches used earlier were having mercury contacts. In
such cases, the actuator moves up and down by means of a plastic float attached to the
actuator by means of a rope or chain. The actuator in turn moves the mercury cartridge
and contacts are initiated due to the angular motion of the mercury contact block /
cartridge. These contacts give electrical signal to the pumps for starting and stopping
operation. In recent past, use of mercury for such applications has been banned due to
environmental hazards. Handling of mercury for disposal and damage of glass cartridge
containing mercury pose safety hazards to the people working with such devices.
Subsequently, electronic level control switches (inductive and capadrJve type) were used
for such applications in place of float switches. In such cases, electrodes are mounted in
the dewatering pit, which are called probes. One of the probe acts as a reference probe
and other probes act as sensing probes. These probes are connected to an electronic
evaluation unit, which continuously monitors the flow of current. Depending on water
level the current flow changes and when the current exceeds the threshold level, a relay
picks up and the pump starts. Similarly, when the current goes below the threshold level
the relay drops. However, in industry the water is contaminated with various chemicals,
oil and grease. In such condition, the reliability of such devices are hampered. In
adverse environmental conditions like fumes/steam/such devices fail to provide desirable
result Hence such devices are found not suitable for application in cable galleries,
furnace cellars, scale channels and similar places.
It would be apparent from the above that presently available conventional float switches,
therefore, have several disadvantages, which include: -
a) such float switches are cost extensive;
b) the mercury type float switches pose environmental and safety hazards;
c) the presently available float switches are difficult to operate and use , especially
the adjustments required are difficult;
d) in case of use of mercury containing glass cartridge, it is susceptible to breakage
and hence unreliable and unsafe;
e) the electronic type float switches presently available have limitations in
application and can not be used for all applications and as such, such switches do
not work reliably due to environmental factors and contamination of water on
liquid;
0 the presently available float switches require frequent maintenance which require
stalling of operation and consequential problems; and
g) moreover, in the presently available float switches the adjustment Is time
consuming.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a liquid level control float
switch system which would avoid the limitations and disadvantages of the presently
available float switches discussed above.
Another object of the present invention is directed to the provision of a liquid level
control float switch system involving a modified cam type float switch adapted for
automatic starting and stopping of pumps used for the purpose of dewatering sump pits
and filling of overhead tanks.
Another object of the present invention is directed to a liquid level control float switch
system which would robust and would not require frequent maintenance and ,therefore,
be conveniently used as a maintenance free float switch for purposes including automatic
starting and stopping of pumps for the purpose of dewatering sump pits and filling of
overhead tanks.
Yet further object of the present invention is to provide for a liquid level control float switch
system that would be simple and user friendly and in which the adjustment would be very
simple and would involve very less stalling.
A further object of the present invention is directed to liquid level control float switch
system adapted to work reliably even in adverse environmental conditions without getting
damaged.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a liquid level
control float switch system comprising:
an actuating lever operatively connected to a float suspended at bottom end through a
chain/wire rope having length to suit maximum/minimum liquid level to be attained;
a counterweight connected to the other top end of said actuating lever to balance said float;
a pair of electrical contacts operatively connected to the pump adapted to put on and off
the pump depending on float position determined by liquid level over a range;
an actuating steel arm adapted to rotate due to up or down movement of the actuating
lever limited by stoppers depending on float position corresponding to liquid level in
sump/tank;
said actuating steel arm providing rotational motion to two cams operatively connected to
said actuating arm such that when said float assumes maximum downward position of the
actuating lever when the tank is empty, said cams assumes a position whereby both said
electrical contacts remain open;
increase in liquid level in said tank/sump favour upward movement of the actuating lever
along with float connected thereto, to first close a contact and when the water level reaches
the predetermined maximum level, the movement of the actuating lever adapted to close
another electrical contact to thereby activate the contactor operatively through said
actuating cams, to switch on the pump operation;
decrease in the liquid level in the said actuating lever traverses downwards along with the
float whereby one said electric contacts open first followed by opening of the said second
electric contacts upon further downward movement of the lever to the minimum level of the
water operatively through said actuating cams to thereby switch off the pump operation.
The said float means comprises plastic/PVC float and said chain/rope length is selectively
provided based on the level of the liquid to be controlled. Also, the said actuating lever
length is selectively provided based on the level of the water to be controlled.
Importantly, a stopper to stop the maximum downward movement of the lever and another
stopper to also stop the maximum upward movement of the lever are provided in the
system.
According to an aspect of control float switch system of the invention wherein the lever
movement is transformed in to the upward and downwards direction to activate/deactivate
the electrical contacts to switch on/off power supply to the pump means comprises
actuating arm adapted to rotate based on the movement of the lever, said rotary motion of
the actuating arm adapted to rotate two cam means which cooperate with the said electrical
contacts for opening and closing the operative connection to the pump depending upon the
water level.
The above disclosed liquid level control float switch system of the invention involving the
cam type float switch is simple and cost effective and provides for advantageous use for
automatic starting and stopping of pumps used for the purpose of dewatering sump pits and
filling of overhead tanks. The system involves simple and yet effective mechanism for
continuous monitoring of the level in tanks / sump pits and activate the pump as and when
required for the purpose of dewatering sump pits and filling of overhead tanks.
The system involving such modified cam type float switch is robust and maintenance free
and involves simple adjustments for effective operations and importantly requires very less
stalling. Importantly, the system is provided such that it can work reliably in any adverse
environment without getting damaged.
It would be thus possible by way of the above disclosed liquid level control float switch
system to provide for simple and cost effective cam based float switch system which
would be user friendly and safe. Importantly, the present system would avoid the
environmental and safety hazards of mercury type float switches which involve
environmental and safety hazards and are also susceptible to breakages and hence are
unreliable and unsafe. The present system which is free of such hazardous components /
constituents is reliable, maintenance free and simple to operate and use requiring very
less adjustment time.
The details of the invention, its object and advantages are explained hereunder in
greater detail in relation to non-limiting exemplary embodiments of the liquid level float
switch systems of the invention as per the accompanying figures.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: shows a simplified a side eievational view of the liquid level control float switch
system in accordance with the present invention with cover dosed;
Figure 2 : illustrates in the top view the liquid level float switch system and its operative
constituents with the cover open ; and
Figure 3: is an illustration of the electrical control circuit diagram used in the liquid level
control float switch system of the present invention.
Reference is first invited to figure 1 which shows the float switch system of the invention
involving the actuating lever (8) which at one end is operarJvely connected to a plastic /
PVC float (13) through chain means (10). At the other end of the actuating lever i.e. the
top end there is provided a counter weight (9). A cover / body casing (5) is provided to
cover the internal operative constituent of the control system.
The detailed operative constituents providing for the lever means based actuation to
provide for the liquid level control is illustrated in greater detail in accompanying figure
2.
As shown in figure 2, the actuating lever (8) is having the plastic PVC float (13) at the
lower end connected through chain means (10) with a counter weight of the actuating
lever (9) provided at the top, with bearings (7) as indicated. To provide for the operative
connection of the lever motion in the upward and downward direction depending upon
the water level with the electrical contacts (1-01) and (2-02), the actuating cam (3,4)
are provided. The actuating lever Asian (6) is also provided as shown.
In figure 3, the electrical control circuit diagram used in the system is illustrated with
indication of the float switch contact (1-01) and (2-02), the contactor of pump motor (C)
and emergency of switch (P).
Reference is further invited to accompanying figures 1 and 2 which illustrate the
operative constituents and the functioning of the liquid level control float switch system
in accordance with the present invention.
The switch with cover of the invention is first placed near the dewatering pit or over the
tank in which water level or liquid level is to be controlled. The plastic / PVC float (13) is
shown suspended through a chain or wire rope (10) with one end of the actuating lever.
The chain length is adjusted depending on the level of the liquid to be controlled. The
length of the actuating lever (8) can be changed depending on the level of water to be
controlled. The float is balanced by a counter weight (9) on the other end of the
actuating lever (8). When the tank is empty due to weight of the float (13), the
actuating lever moves down and the maximum movement is limited by the stopper
(12). This causes rotational movement of a square type actuating steel arm (13), which
rotates the two plastic cams (3, 4).
When the tank is empty, the cams are adjusted such that both electrical contacts (1-01)
and (2-02) remain open. The level of the water increases, the float (13) comes in
contact with water and chain slackens. Gradually due to counter weight (9), the
actuating lever starts moving up (from float end) and contact on (2-02) doses first.
When the water level further increases and reaches the determined level (max) contact
(1-01) doses and contactor of the pump picks up and pump starts. The max upward
movement of the actuating lever is restricted by the stopper (9).
When the water level starts decreasing the actuating lever starts moving down (float
end). In this direction of movement, the electrical contact (1-01) opens first On further
emptying of the tank the lever will go downwards. When the water level reaches the
minimum level, the contact (2-02) also opens. At this point, the pump will stop.
The above operation of the liquid level control float switch system of the invention
ensures smooth operation of the pump in a particular range. It also avoids frequent,
unnecessary starting and stopping of the pump. Hence, the system is directed to
increase life of equipment and is reliable and safe for wide scale application and use
especially for the purposes of dewatering of sump pits and filling of overhead tanks and
other similar applications. The float switch system which is robust and would not require
frequent maintenance is , therefore, convenient to use and is a maintenance free float
switch involve very less stalling. Importantly, also the liquid level control float switch
system is adapted to work reliably even in adverse environmental conditions without
getting damaged thereby ensuring durability and reliability of the system.
We Claim:
1. A liquid level control float switch system comprising:
an actuating lever operatively connected to a float suspended at bottom end through
a chain/wire rope having length to suit maximum/minimum liquid level to be
attained;
a counterweight connected to the other top end of said actuating lever to balance
said float;
a pair of electrical contacts operatively connected to the pump adapted to put on
and off the pump depending on float position determined by liquid level over a
range;
an actuating steel arm adapted to rotate due to up or down movement of the
actuating lever limited by stoppers depending on float position corresponding to
liquid level in sump/tank;
said actuating steel arm providing rotational motion to two cams operatively
connected to said actuating arm such that when said float assumes maximum
downward position of the actuating lever when the tank is empty, said cams
assumes a position whereby both said electrical contacts remain open;
increase in liquid level in said tank/sump favour upward movement of the actuating
lever along with float connected thereto, to first close a contact and when the water
level reaches the predetermined maximum level, the movement of the actuating
lever adapted to close another electrical contact to thereby activate the contactor
operatively through said actuating cams, to switch on the pump operation;
decrease in the liquid level in the said actuating lever traverses downwards along
with the float whereby one said electric contacts open first followed by opening of
the said second electric contacts upon further downward movement of the lever to
the minimum level of the water operatively through said actuating cams to thereby
switch off the pump operation.
2. A liquid level control float switch system as claimed in claim 1 wherein said float
comprises plastic/PVC float.
3. A liquid level control float switch system as claimed in anyone of claims 1 or 2
wherein said chain/rope length is selectively provided based on the level of the liquid
to be controlled.
4. A liquid level control float switch system as claimed in anyone of claims 1 to 3
wherein said actuating lever length is selectively provided based on the level of the
water to be controlled.
5. A liquid level control float switch system as claimed in anyone of claims 1 to 4
comprising a stopper to stop the maximum downward movement of the lever and
another stopper to also stop the maximum upward movement of the lever.
6. A liquid level control float switch system as claimed in anyone of claims 1 to 5
wherein the lever movement is transformed in to the upward and downwards
direction to activate/deactivate the electrical contacts to switch on/off power supply
to the pump means comprises actuating arm adapted to rotate based on the
movement of the lever, said rotary motion of the actuating arm adapted to rotate
two cam means which cooperate with the said electrical contacts for opening and
closing the operative connection to the pump depending upon the water level.
7. A liquid level control float switch system as claimed in anyone of claims 1 to 6
wherein said actuating arm comprise square type steel actuating arm and said cam
means comprise plastic cams.
8. A liquid level control float switch system substantially as herein described and
illustrated with reference to the accompanying figures.

A liquid level control float switch system which avoids the complexities and
disadvantages, of presently available float switches which apart from being cost
extensive are basically the mercury type float switches which pose environmental
and safety hazards and are also difficult to operate. The liquid level control float
switch system includes an actuating lever and float means through a chain /wire
rope;a counterweight to balance the said float means; electrical contact means
operatively connected to the pump means adapted to put on and off the pump, said
float means providing for downward motion of the actuating lever when the tank is
empty ,cooperating cam means operatrvely connected to said lever arm such that
when the tank is empty the said cams are selectively adjusted to assume a position
whereby both said electrical contacts remain open. The system is simple to obtain,
safe and user friendly.