FORM-2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
PROVISIONAL SPECIFICATION
(See section 10 and Rule 13)
PUMPS
KIRLOSKAR BROTHERS LIMITED
An Indian Company
of Udyog Bhavan, Tilak Road, Pune-411002,
Maharashtra, India.
THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION

FIELD OF INVENTION
This invention relates to Pumps.
In particular, this invention relates to centrifugal pumps. More particularly, this invention relates to priming of centrifugal pumps.
INTRODUCTION
A pump is a device used to move fluids or slurries. A pump moves liquids from one place to another place, by adding energy to the system to overcome frictional resistance encountered in the pipe line and increase the potential energy.
Pumps can be broadly classified, based on the method of moving a liquid, into two major groups:
(1) Roto-dynamic pumps and
(2) Positive displacement pumps.
Roto-dynamic pumps are based on impellers which rotate within the liquid to impart a tangential acceleration to the liquid and a consequent increase in the energy of the liquid. This energy is used to pump the liquid to higher elevation for storage or consumption.
A positive displacement pump causes a liquid to move by trapping a fixed amount of liquid and then forcing (displacing) that trapped volume into the discharge pipe.
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Positive displacement pumps can be further classified as either rotary-type (rotary vane pump) or reciprocating-type (diaphragm pump).
Centrifugal Pumps are roto-dynamic pumps which convert mechanical energy into hydraulic energy by centripetal force on the liquid. Typically, a rotating impeller increases the velocity of the liquid. The casing, or volute, of the pump then acts to convert this increased velocity into an increase in pressure. As the mechanical energy is converted into a pressure head by centripetal force, the pump is classified as centrifugal. Such pumps are found in virtually every industry, and in domestic service in developed countries for washing machines, dishwashers, swimming pools, and water supply.
Typically these centrifugal pumps are used for transferring fluids such as water from a lower level such as an underground tank, well, river to a higher point for storage, consumption and or for dewatering flooded areas. The level difference may be marginal or significant. Where the centrifugal pump and the source of water is approximately at the same level or if the source is higher, there is a continuous supply of fluid such as water at the inlet side of the pump. This is known as a flooded inlet condition. Under such conditions a centrifugal pump will deliver water as soon as the prime mover (electric motor, engine and such) is started.
However in some cases centrifugal pump is installed at a height above the liquid level and a flexible or rigid pipe is used to connect the liquid in the liquid source to the pump. This is connecting pipe is known as inlet or suction pipe. The suction pipe and the pump casing have to be filled with the liquid at the starting stage before the motor or engine is started for the pump
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to commence delivery of the liquid. This act of filling liquid in the suction pipe is known as priming. If the level of the liquid is below the impeller (improper priming) and in this condition the prime mover is switched on, the pump will not deliver any liquid out put. This is known as dry running of the pump. Prolonged dry running of a centrifugal pump damages gland packing, bearings and may also damage the impeller.
Priming of small domestic or industrial stationary pump is done manually by opening a plug provided on the pump casing and pouring liquid into the pump. Such pumps are provided with a foot valve at the lower most portion of the suction pipe, dipping into the liquid, to retain the liquid in the suction pipe. After closing the plug the drive unit like electric motor or engine is started and a properly primed centrifugal pump will commence transferring liquid from the source point to the delivery/ storage point. If the priming was incomplete or the foot valve leaking, the pump will not commence delivering the liquid, leading to dry running of the pump. At this stage the drive unit has to be switched off and the pump re-primed before starting the drive unit.
In mobile, large capacity pump units and especially where the suction side is a flexible pipe, it is not easy to prime the pump properly. This led to the development of various methods to facilitate easy and quick priming centrifugal pumps. One of the common methods used to achieve quick priming of the pump is to install a small storage tank, at a level above the pump casing, on the delivery side of the pump and draw liquid from the tank to prime the pump by opening and closing of valves. This tank is kept filled by taking a tapping from the delivery pipe line of the pump and using a float
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controlled valve to prevent over flowing and spillage. This operation could be manually carried out or automated through use of solenoid controlled valves and programmable logic controllers.
PRIOR ART
Some of the methods suggested for priming a centrifugal pump in the prior art and their demerits are described herein under:
US Patent 5536147 discloses a "Vacuum priming system for centrifugal pumps". This invention uses a separate vacuum pump to evacuate the suction pipe and draw the liquid up to the impeller level. Once the impeller is fully flooded a control valve connects the vacuum pump to the atmosphere. This invention uses an electronic control module with level sensing switches and solenoid operated control valves to prime the pump and protect the vacuum pumps from flooding. Electronic control module requires power supply and battery backup and may be affected by weather condition in outdoor service conditions.
US Patent 5795127 discloses a "Vertical shaft self-priming centrifugal pump". The pump of this invention requires a semi-flooded in let and a semi open impeller to achieve self priming and cannot be used in applications where the pump has to be installed at a level higher than the liquid level.
US Patent 6071072 discloses a "Self-Priming centrifugal pump" having a suction pipe with a liquid trap arrangement which will trap part of the liquid and use the same as priming liquid for the next operation. Also provided is a
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liquid air separation unit and recirculation tube that permits the repeated use of trapped liquid to enhance the suction of the pump for self priming. This pump is not suitable for mobile applications as trapped water may leak during transportation.
OBJECTS OF THE INVENTION
One of the objects of this invention is to provide a centrifugal pump that is capable of auto-priming.
Another object of this invention is to provide an Auto-priming centrifugal pump that is suitable for applications where priming is to be done instantaneously, like for fire fighting applications
Another object of this invention is to provide an Auto-priming centrifugal pump that is portable.
Yet another object of this invention is to provide an Auto-priming centrifugal pump that is suitable for dewatering applications like mobile dewatering & irrigation sets.
Another object of this invention is to provide an Auto-priming centrifugal pump that is that is simple to operate and does not require complicated electronic controls to achieve priming.
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Yet another object of this invention is to provide an Auto-priming centrifugal pump that may be engine driven and does not require electricity to achieve priming.
SUMMARY OF THE INVENTION:
This invention envisages the use of a vacuum pump as a priming unit. The priming unit can be driven by advantageously mounting it on the main drive shaft as a coaxial shaft or by a drive mechanism using a belt pulley mounted on both the shafts. As the prime mover is switched on the pump shaft starts turning, rotating the pump impeller and also the vacuum pump. The vacuum pump removes air in the pump casing as well as suction pipe and creates partial vacuum in the casing & suction pipe/pipe fittings. At this stage delivery side non return valve prevents ingress of air from the delivery side pipe line into the pump casing. Atmospheric pressure forces the liquid to rise up in the suction pipe and submerge the impeller. When the suction side is fully flooded with pumped liquid the pump starts delivering the liquid. As the level of liquid rises a float provided in the primary tank rises and seals of the vacuum pump inlet thus preventing liquid from entering the vacuum pump. Once the pump is properly primed and commences delivery the drive mechanism of the priming unit may disconnected from the main shaft by suitable disengagement clutch.
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BRIEF DESCRIPTION OF THE DRAWING:
All the aspects and advantages of the invention will become apparent with the description of the preferred, non-limiting embodiment, when read together with the accompanying drawing, in which:
Figure 1 is the schematic diagram of the auto-priming centrifugal pump of this invention.
DETAILED DESCRIPTION OF THE DRAWING:
Referring to the accompanying drawing, the auto-priming centrifugal pump of this invention is indicated generally by the reference numeral 100. Referring to figure 1, the auto-priming centrifugal pump of this invention consist of impeller (10), mounted on the pump shaft (not specifically shown), pump casing (12) of volute inner profile, shaft packing (14), non return valve (16), back priming line (18), primary tank (20), float(22), vacuum control valve (24), air filter 26, back flush valve (28) and auto secondary tank dump valve and pipe (30). Suction in let (50) and vacuum pump connection (60) is also indicated.
When the prime mover is started the vacuum pump (not specifically shown) connected to the connection (60) also starts as it is coupled to the main drive shaft of the pump. At this stage the suction pipe line connected to the suction side (50) of the pump is filled with air. The float (22) is in its lower most position due to its self weight keeping the vacuum control valve (24) in fully open position. As the vacuum pump sucks the air out the pump casing the non return valve (16) blocks entry of air from the delivery side pipe, creating partial vacuum in the pump casing.
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Atmospheric pressure forces the liquid to rise in the suction pipe line and reach the pump casing through inlet (50).
As soon as the impeller is submerged in the liquid the pump starts developing positive pressure within the casing. This pressure lifts the non return valve 16 and the pump starts to deliver liquid.
As the liquid fills in the primary tank 20, the float lifts due to hydrostatic pressure of the liquid and seals the vacuum control valve and stop further rise in the water level and thereby prevent water from entering the vacuum pump.
While considerable emphasis has been placed herein on the particular features of an, auto-priming centrifugal pump, the improvisation with regards to it, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiment without departing from the principles of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

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