Title of Invention

AN OIL DRAINING MECHANISM IN THE CRANKSHAFT OF A HERMETICALLY SEALED COMPRESSORS

Abstract

An oil draining mechanism in the crankshaft of a hermetically sealed compressors, said mechanism consisting of a central bore provided in the crankshaft and a spiral groove formed on the face of the crankshaft for drawing lubricating oil from the oil sump of the compressor for lubricating its main bearing, said spiral groove terminating at the bearing end in a drain passage which drain passage communicates internally with the central bore leading to the oil sump.

Full Text

FORM-2 THE PATENTS ACT, 1970 {39 of 1970) COMPLETE Specification SECTION -10, rule 13 AN OIL DRAINING MECHANISM IN THE CRANKSHAFT OF A HERMETICALLY, SEALED COMPRESSORS THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:- This invention relates to an oil draining mechanism in the crankshaft of a hermetically sealed compressors. This invention particularly relates to oil draining mechanism in hermetic sealed compressors. More particularly the present invention relates to a novel arrangement for draining lubricating oil creeping up the crank shaft. Hermetic Sealed compressors are used to compress low pressure vapor from evaporator & deliver high pressure & high temperature vapor to condenser. In a typical hermetic compressor suction gas enters in the shell cavity through a suction tube which is sucked in the suction muffler due to suction stroke of piston. The gas flows to cylinder bore via a suction plenum in the cylinder head through a passage in the crankcase or connecting tubes between suction muffler & cylinder head & suction port in the valve plate. This low pressure gas is compressed to high pressure & delivered to discharge muffler via a discharge port in the valve plate to cylinder head plenum. In the discharge plenum gas is attenuated and delivered to condenser of appliance through a discharge tube connected to the discharge muffler by a discharge shock loop. The hermetic compressor generally comprises a lower and upper shell, inside which three or more resilient members hold the pump assembly (coil springs). The whole assembly 2 body is supported by legs, which are attached to a shell. The compressor pump assembly consists of motor component stator and rotor and gas compressor mechanism. The rotor is fitted directly on the crankshaft. The stator is mounted on the crankcase through fasteners. The crankshaft is housed in the main bearing provided in the crankcase. The power required for rotation of the crankshaft is given by a motor. The hermetic compressor generally comprises a 2-pole Induction motor as the prime mover. In the hermetically sealed refrigeration compressor, gas enters through the suction tube and travels into the shell, which surrounds the pump assembly. The gas is further picked up by the suction pick up tube and led into the crankcase, which then goes into the suction plenum in the cylinder head through suction mufflers, which are in built in the crank case. Inside, the motor and pump assembly are cooled by refrigerant available inside the shell cavity. In this process the refrigerant picks-up heat from these (motor and pump assembly) hotter components before it reaches in to the crankcase by heat convection. It is well known from basics of thermodynamics that suction gas super heating will result in reduced compressor performance as density of gas reduces with increased temperature which means less mass flow rate in to the cylinder bore. 3 The reciprocating mechanism used to compress the refrigerant generates a lot of pulses which if allowed to act directly on the gas cavity leads to vibration of the compressor and/or generates noise. Usually a pulse attenuator /muffler becomes necessary on both suction and discharge side of the pumping mechanism to take care of this effect. Generally these mufflers are in built in the crankcase, which is of a highly conductive material, or are fitted as separate metallic components, which are good thermal conductors. The suction gas passes through these conventional gas passages either separate or in built in the crankcase and in so doing picks up heat from the surrounding hotter bodies before it reaches to bore. This is undesirable. Suction & discharge mufflers are used for attenuation of gas pulsation. When it attenuates noise & vibration, pressure drop is observed in the mufflers. This pressure drop will result in low mass flow rate as suction gas specific volume increases as pressure decreases thus reducing cooling capacity of compressor. The pressure drop is of about 1 psi as the suction gas passes through the muffler. This pressure drop results in decrease in the velocity of the gas and its consequent expansion. An oil sump is provided at the lower end. Rotation of the crank shaft causes Lubricating oil to be drawn up from the 4 sump which lubricates the main bearing and other components fitted to the crank shaft. Lubricating oil. from the main bearing tends to trickle out along the shaft and enter the suction chamber along the outer walls of the mairt bearing.* A spiral groove on the outer circumferential wall of the crank shaft is provided in the prior art which tends to lead the excess oil from the main bearing upwards and into the suction chamber area. According to this invention there is provided an oil draining mechanism in the crankshaft of a hermetically sealed compressors, said mechanism consisting of a central bore provided in the crankshaft and a spiral groove formed on the face of the crankshaft for drawing lubricating oil from the oil sump of the compressor for lubricating its main bearing, said spiral groove terminating at the bearing end in a drain passage well below the operative upper end of the main bearing and which drain passage communicates internally with the central bore leading to the oil sump. In accordance with a preferred embodiment of this invention the spiral groove extends for 270 degrees on the face of the crankshaft. The invention will now be described with reference to the accompanying drawings, in which 5 Figure 1 is the front perspective view of the configuration in accordance with the prior art; Figure 2 is the flow chart of the operation steps in accordance with the prior art; Figure 3 is the arrangement envisaged in accordance with this invention; and Figure 4 is the flow chart of the operation steps in accordance with this invention. Referring to the drawings; in figure 1 is seen the configuration of the oil draining hole in the prior art. On the crankshaft 1 of a hermetically sealed compressor moving in a crankcase 4, there is provided a groove 2. A passage 6 through the crankshaft 1 extends between an oil sump 100 to an orifice 8 at the operative lower extremity of the groove 2. Rotation of the crankshaft 1 causes oil to be picked up from the oil sump 100 and to flow via the passage 6 and the spiral groove 2 to the main bearing bush 7 . From the main bearing oil trickles into the suction bowl 6. From the suction bowl oil is transferred to the oil sump 100 via the suction hole 1 and a passage 9. In the arrangement as seen in figure 1 of the drawings, there is no drain passage for the oil and therefore a significant amount of oil mixes with the suction gas in the suction bowl. The groove/z^n the shaft 5 is made for the entire three hundred and sixty degrees. The 6 percentage of oil circulating in the system is about 7 percent. The oil picks up heat as it flows from the crankcase bowl after picking up heat from the main bearing 7. The suction gas picks up heat from the oil and gets superheated. This results in loss of cooling capacity. The flow chart of the steps of the movement of the oil is seen in figure 2 of the drawings. As seen in figure 2, the suction gas mixes with the oil in the bowl. Seen in figure 3 is the geometry of the shaft in accordance with this invention. In figure 3, the spiral groove A 3) is pfiA 'I Reduced in length to 270 degrees. The crank shaft 5 isj. provided with a central bore/15 \nd the spiral groove 13 germinates in a passage 12 which leads into this central bore gi"5 leading into the oil sump 100. The arrows marked 14 represent the oil flowing back to the sump 100. Almost no oil enters the bowl and therefore the flow chart of the operations is as seen in figure 4 of the drawings. There is therefore separation of the lubricating oil from the gas pathway. Thus in the arrangement shown in figure 3 the spiral groove 13 is truncated before it enters the suction chamber area and below the main bearing housing. The drain passage 12 is provided at the upper end of the spiral groove 13 seen in Figure 3. This hole 12 communicates with the central lubricating oil bore 15 which acts as a passage in the crank shaft 5 and leads the oil shown by arrows 14 from the spiral 7 groove 13 directly into the oil sump 100 located below the short end of the crank shaft 5 in its operative configuration. There is no compromise on the lubrication for the main bearing at the same time the circulating oil drops down to 1 percent. The oil which takes up heat from the bearing now flows back to the oil sump. This hot oil does not contact the suction gas thus reducing superheating and improving cooling capacity of 1.5 per cent. While the present invention has been described herein with reference to a specific embodiment thereof, it is contemplated that the present invention is not limited thereby and various changes and modifications may be made therein for those skilled in the art without departing from the scope of the invention. 8 We Claim: 1] An oil draining mechanism in the crankshaft of a hermetically sealed compressors, said mechanism consisting of a central bore provided in the crankshaft and a spiral groove formed on the face of the crankshaft for drawing lubricating oil from the oil sump of the compressor for lubricating its main bearing, said spiral groove terminating at the bearing end in a drain passage which drain passage communicates internally with the central bore leading to the oil sump. 2] An oil draining mechanism in the crankshaft of a hermetically sealed compressors, as claimed in claim 1, in which the spiral groove on the face of the crank shaft extends to 270 degrees. 3] An oil draining mechanism in the crankshaft of a hermetically sealed compressors as described herein with reference to figures 3 and 4 of the drawings. 9 Dated this lstth day of April 2003

Documents:

36-mum-2002-cancelled pages(11-08-2003).pdf

36-mum-2002-claims(granted)-(11-08-2003).pdf

36-mum-2002-claims(granted)-(11-8-2003).doc

36-mum-2002-correspondence(22-01-2007).pdf

36-mum-2002-correspondence(ipo)-(19-10-2004).pdf

36-mum-2002-drawing-(04-04-2003).pdf

36-mum-2002-form 1(15-01-2002).pdf

36-mum-2002-form 13(22-01-2007).pdf

36-mum-2002-form 19(23-05-2003).pdf

36-mum-2002-form 2(granted)-(11-08-2003).pdf

36-mum-2002-form 2(granted)-(11-8-2003).doc

36-mum-2002-form 26(05-12-2006).pdf

36-mum-2002-form 3(15-01-2002).pdf

36-mum-2002-form 4(03-04-2003).pdf

36-mum-2002-form 5(04-04-2003).pdf

36-mum-2002-power of attorney(15-01-2002).pdf

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