Indian Patents. 269869:PISTON RING PACK FOR REDUCED BLOW-BY, OIL CARRY OVER AND RING WEAR IN A RECIPROCATING TYPE AIR COMPRESSOR OF A MOTOR VEHICLE BRAKING SYSTEM

Title of Invention	PISTON RING PACK FOR REDUCED BLOW-BY, OIL CARRY OVER AND RING WEAR IN A RECIPROCATING TYPE AIR COMPRESSOR OF A MOTOR VEHICLE BRAKING SYSTEM
Abstract	A piston ring pack for reduced blow-by and ring wear in a reciprocating type air compressor of a motor vehicle braking system, comprising a top ring, a second ring and a third ring, wherein the top ring is a micro Napier ring of a predetermined

Full Text	This invention relates to a piston ring pack for reduced blow-by, oil carry over and ring wear in a reciprocating type air compressor of a motor vehicle braking system. A reciprocating air compressor comprises a piston and cylinder arrangement with a cylinder head assembly over the cylinder. The cylinder head assembly comprises cylinder head, inlet valve and delivery valve assemblies. To facilitate port connection and free air flow, suitable inlet and delivery ports are provided in cylinder head. The inlet valve opens during suction stroke of the piston and the delivery valve opens during the delivery stroke of the piston. The air compressor sucks air at atmospheric or relatively low pressure through the holes in the inlet valve, compresses it to higher pressure and delivers the compressed air through the delivery holes in delivery valve. The piston ring pack used in a reciprocating air compressor consists of two compression rings and one oil control ring. The functions of piston rings are: 1. To seal air pressure 2. To control oil carry over by scraping oil from the cylinder walls. During the rotation of crankshaft, oil will be splashed onto cylinder bore and it lubricates piston rings and cylinder. Excess oil in the cylinder bore is scrapped back in to crankcase by oil control ring. Still minimum lubricating oil Page 2 of 11 layer will be present on the cylinder bore and that lubricates sliding contact of compression ring and cylinder bore. During suction stroke of the compressor, there is a possibility of oil to pass over the compression rings/ cylinder bore, compression ring/piston groove clearances in to compression chamber. The oil that is escaped in to piston bore through the compression rings is called "Oil carry over". High oil carry over in compressors will have detrimental effects on downstream brake products. Hence oil carry over should be minimized. During compression stroke of the piston, there is a possibility of high pressure air to escape through the compression rings/ cylinder bore, compression rings/piston groove clearances to crankcase. The air that comes in to crank case during compression stroke of piston is called "Blow by". High blow by in compressors will reduce air delivery of the compressors and also may have detrimental effects on engine. To reduce blow by, the conventional method is to use a plain compression ring. However, while using a plain compression ring, after some field usage, there is a possibility of high oil carry over because of ring twist. Hence the contradiction is when the piston ring pack is optimized for oil carry over, blow by will be high. When the ring pack is optimized for blow by oil carry over will be high after certain field usage. Generally, the piston ring pack may consist of two Napier rings and one oil control ring or one plain compression ring, one Napier ring and one oil 3 Page 3 of 11 control ring. Napier ring will have a recess at the lower edge that helps in better oil scraping. While using two Napier rings and one oil control ring, oil scraping will be better but blow by will be high after some field usage. While using one plain compression ring, one Napier ring and one oil control ring, better blow by can be achieved. However after some field usage, oil scraping efficiency will come down. The present invention of compression ring with optimized ring profile and tangential tension reduces oil carry over, blow by and ring wear. The first ring is a plain compression ring provided with a 'very small recess' called as "Micro Napier ring" with optimized tangential tension. This reduces the ring twist to a great extent and thus reduces the oil carry over and blow by. The micro Napier ring profile retains the 'scraping edge' of the compression ring for a longer period of field usage condition, there by good oil control is maintained. The second compression ring is a Napier ring with an optimized ring profile and tangential tension to reduce oil carry over, blow by and ring wear. The advantages of present invention are: 1. Reduced blow- by 2. Reduced oil carry over 3. Increased life of piston ring Page 4 of 11 This invention will now be described with reference to the accompanying drawings, which illustrate by way of example, and not by way of limitation, one of several possible embodiments of the micro Napier compression ring proposed herein. Figure 1 - illustrates the sectional view of the cylinder head and piston assembly of the air compressor with conventional piston ring pack. Figure 2 - illustrates the sectional view of the piston assembly with ring pack of the embodiment Figure 3 - illustrates the sectional view of the top micro Napier ring of the embodiment Figure 4 - illustrates the sectional view of the second Napier ring of the said embodiment Figure 1 Referring to figurel, the reciprocating air compressor known to the art consists of a cylinder (A), piston (B) moving within the bore of the said cylinder with the cylinder head assembly (C) fixed to the said cylinder. The piston assembly consists of a piston (B), three piston rings (J, L, K) and gudgeon pin (E). The piston assembly is assembled to the connecting rod (F) by inserting the gudgeon pin (E) into the bore of the connecting rod (F). The entire piston assembly slides into the bore of the cylinder (A). The space above the piston (B) constitutes the compression chamber and the space below the piston (B) constitutes the lubrication chamber. Pages of 11 The compressor sucks air during the suction stroke and compresses air during the compression stroke inside the compression chamber. The compressed air is delivered through delivery port of cylinder head (C). By using two Napier ring's (J, L) as compression rings in the piston ring pack, blow-by will be high because of reduced contact land between ring running face and cylinder (A) due to higher running face taper angle. By using plain compression ring as top ring and Napier ring as second ring, the oil carry over will be high because of absence of oil scraping edge in plain compression ring. The very objective of this invention is to overcome the deficiencies of prior art. Figure 2 The deficiencies of prior art are overcome by incorporating a piston ring pack with top ring as micro Napier ring (D), second ring as Napier ring (J) and third ring as oil control ring (K). The top ring called as micro Napier ring (D) reduces blow-by and oil carry over because of optimized ring profile. The wear of micro Napier ring is reduced because of optimized tangential tension. The second ring called as Napier ring (J) reduces oil carry over because of optimized ring profile. The wear of Napier ring is reduced because of optimized tangential tension. The third ring called as oil control ring (K) effectively scrapes oil from cylinder walls. Pages of 11 Figure 3 The top ring called as micro Napier ring (D) reduces blow-by and oil carry over because of presence of small recess (H). This small recess (H) reduces the ring twist to a great extent and thus reduces the oil carry over and blow by. The micro Napier ring profile retains the 'scraping edge' (N) of the compression ring for a longer period of field usage condition, there by good oil control is maintained. Due to its optimized running face (G) taper angle and tangential tension, the wear of ring is less thereby increasing life of piston ring. Figure 4 The second ring called as Napier ring (J) controls oil carry over because of presence of oil scraping edge (I). The recess (M) in the ring causes it to twist and makes contact with the cylinder, controlling blow-by. The wear of Napier ring is reduced because of optimized tangential tension. From the foregoing description it will be observed that this invention is not confined to the specific embodiment illustrated and described, but that various other embodiments thereof are possible without departing from its scope and ambit. We claim: 1. A piston ring pack for reduced blow-by and ring wear in a reciprocating type air compressor of a motor vehicle braking system, comprising a top ring, a second ring and a third ring, wherein the top ring is a micro Napier ring of a predetermined optimised ring twist together with a running face taper angle and tangential tension for reducing blow-by, oil carry over and ring wear; the second ring is a Napier ring of a predetermined optimised running face taper angle and tangential tension, for controlling oil carry over and reducing ring wear; and the third ring is a oil control ring for effectively scraping oil from the cylinder wall of the said compressor. 2. A piston ring pack for reduced blow-by and ring wear in a reciprocating type air compressor of a motor vehicle braking system, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Full Text

This invention relates to a piston ring pack for reduced blow-by, oil carry over and ring wear in a reciprocating type air compressor of a motor vehicle braking system.
A reciprocating air compressor comprises a piston and cylinder arrangement with a cylinder head assembly over the cylinder. The cylinder head assembly comprises cylinder head, inlet valve and delivery valve assemblies. To facilitate port connection and free air flow, suitable inlet and delivery ports are provided in cylinder head. The inlet valve opens during suction stroke of the piston and the delivery valve opens during the delivery stroke of the piston. The air compressor sucks air at atmospheric or relatively low pressure through the holes in the inlet valve, compresses it to higher pressure and delivers the compressed air through the delivery holes in delivery valve.
The piston ring pack used in a reciprocating air compressor consists of two compression rings and one oil control ring. The functions of piston rings are:
1. To seal air pressure
2. To control oil carry over by scraping oil from the cylinder walls. During the rotation of crankshaft, oil will be splashed onto cylinder bore
and it lubricates piston rings and cylinder. Excess oil in the cylinder bore is scrapped back in to crankcase by oil control ring. Still minimum lubricating oil
Page 2 of 11

layer will be present on the cylinder bore and that lubricates sliding contact of compression ring and cylinder bore.
During suction stroke of the compressor, there is a possibility of oil to pass over the compression rings/ cylinder bore, compression ring/piston groove clearances in to compression chamber. The oil that is escaped in to piston bore through the compression rings is called "Oil carry over". High oil carry over in compressors will have detrimental effects on downstream brake products. Hence oil carry over should be minimized.
During compression stroke of the piston, there is a possibility of high pressure air to escape through the compression rings/ cylinder bore, compression rings/piston groove clearances to crankcase. The air that comes in to crank case during compression stroke of piston is called "Blow by". High blow by in compressors will reduce air delivery of the compressors and also may have detrimental effects on engine.
To reduce blow by, the conventional method is to use a plain compression ring. However, while using a plain compression ring, after some field usage, there is a possibility of high oil carry over because of ring twist.
Hence the contradiction is when the piston ring pack is optimized for oil carry over, blow by will be high. When the ring pack is optimized for blow by oil carry over will be high after certain field usage.
Generally, the piston ring pack may consist of two Napier rings and one oil control ring or one plain compression ring, one Napier ring and one oil
3 Page 3 of 11

control ring. Napier ring will have a recess at the lower edge that helps in better oil scraping.
While using two Napier rings and one oil control ring, oil scraping will be better but blow by will be high after some field usage.
While using one plain compression ring, one Napier ring and one oil control ring, better blow by can be achieved. However after some field usage, oil scraping efficiency will come down.
The present invention of compression ring with optimized ring profile and tangential tension reduces oil carry over, blow by and ring wear. The first ring is a plain compression ring provided with a 'very small recess' called as "Micro Napier ring" with optimized tangential tension. This reduces the ring twist to a great extent and thus reduces the oil carry over and blow by. The micro Napier ring profile retains the 'scraping edge' of the compression ring for a longer period of field usage condition, there by good oil control is maintained. The second compression ring is a Napier ring with an optimized ring profile and tangential tension to reduce oil carry over, blow by and ring wear. The advantages of present invention are:
1. Reduced blow- by
2. Reduced oil carry over
3. Increased life of piston ring
Page 4 of 11

This invention will now be described with reference to the accompanying drawings, which illustrate by way of example, and not by way of limitation, one of several possible embodiments of the micro Napier compression ring proposed herein.
Figure 1 - illustrates the sectional view of the cylinder head and piston assembly of the air compressor with conventional piston ring pack.
Figure 2 - illustrates the sectional view of the piston assembly with ring pack of the embodiment
Figure 3 - illustrates the sectional view of the top micro Napier ring of the embodiment
Figure 4 - illustrates the sectional view of the second Napier ring of the said embodiment Figure 1
Referring to figurel, the reciprocating air compressor known to the art consists of a cylinder (A), piston (B) moving within the bore of the said cylinder with the cylinder head assembly (C) fixed to the said cylinder.
The piston assembly consists of a piston (B), three piston rings (J, L, K) and gudgeon pin (E). The piston assembly is assembled to the connecting rod (F) by inserting the gudgeon pin (E) into the bore of the connecting rod (F). The entire piston assembly slides into the bore of the cylinder (A). The space above the piston (B) constitutes the compression chamber and the space below the piston (B) constitutes the lubrication chamber.
Pages of 11

The compressor sucks air during the suction stroke and compresses air during the compression stroke inside the compression chamber. The compressed air is delivered through delivery port of cylinder head (C).
By using two Napier ring's (J, L) as compression rings in the piston ring pack, blow-by will be high because of reduced contact land between ring running face and cylinder (A) due to higher running face taper angle. By using plain compression ring as top ring and Napier ring as second ring, the oil carry over will be high because of absence of oil scraping edge in plain compression ring. The very objective of this invention is to overcome the deficiencies of prior art. Figure 2
The deficiencies of prior art are overcome by incorporating a piston ring pack with top ring as micro Napier ring (D), second ring as Napier ring (J) and third ring as oil control ring (K).
The top ring called as micro Napier ring (D) reduces blow-by and oil carry over because of optimized ring profile. The wear of micro Napier ring is reduced because of optimized tangential tension.
The second ring called as Napier ring (J) reduces oil carry over because of optimized ring profile. The wear of Napier ring is reduced because of optimized tangential tension.
The third ring called as oil control ring (K) effectively scrapes oil from cylinder walls.
Pages of 11

Figure 3
The top ring called as micro Napier ring (D) reduces blow-by and oil carry over because of presence of small recess (H). This small recess (H) reduces the ring twist to a great extent and thus reduces the oil carry over and blow by. The micro Napier ring profile retains the 'scraping edge' (N) of the compression ring for a longer period of field usage condition, there by good oil control is maintained. Due to its optimized running face (G) taper angle and tangential tension, the wear of ring is less thereby increasing life of piston ring. Figure 4
The second ring called as Napier ring (J) controls oil carry over because of presence of oil scraping edge (I). The recess (M) in the ring causes it to twist and makes contact with the cylinder, controlling blow-by. The wear of Napier ring is reduced because of optimized tangential tension.
From the foregoing description it will be observed that this invention is not confined to the specific embodiment illustrated and described, but that various other embodiments thereof are possible without departing from its scope and ambit.

We claim:
1. A piston ring pack for reduced blow-by and ring wear in a reciprocating type air compressor of a motor vehicle braking system, comprising a top ring, a second ring and a third ring, wherein the top ring is a micro Napier ring of a predetermined

optimised ring twist together with a running face taper angle and tangential tension for reducing blow-by, oil carry over and ring wear; the second ring is a Napier ring of a predetermined optimised running face taper angle and tangential tension, for controlling oil carry over and reducing ring wear; and the third ring is a oil control ring for effectively scraping oil from the cylinder wall of the said compressor. 2. A piston ring pack for reduced blow-by and ring wear in a reciprocating type air compressor of a motor vehicle braking system, substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Documents:

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Patent Number

269869

Indian Patent Application Number

1585/CHE/2009

PG Journal Number

47/2015

Publication Date

20-Nov-2015

Grant Date

13-Nov-2015

Date of Filing

03-Jul-2009

Name of Patentee

WABCO-TVS (INDIA) LIMITED

Applicant Address

JAYALAKSHMI ESTATES, 8 HADDOWS ROAD, CHENNAI - 600 006

Inventors:

#	Inventor's Name	Inventor's Address
1	SUNDARAMAHALINGAM SELVAMANI	JAYALAKSHMI ESTATES, 8 HADDOWS ROAD, CHENNAI - 600 006
2	SIMON LEONARD	JAYALAKSHMI ESTATES, 8 HADDOWS ROAD, CHENNAI - 600 006
3	PATEL SRINIVAS	JAYALAKSHMI ESTATES, 8 HADDOWS ROAD, CHENNAI - 600 006

PCT International Classification Number

B60T8/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA