Title of Invention

PISTON WITH EXTENDED SURFACE FOR IMPROVED COOLING EFFICIENCY FOR AIR COMPRESSOR IN A MOTOR VEHICLE BRAKING SYSTEM

Abstract

This invention relates to piston configuration for improved cooling efficiency for an air compressor in a motor vehicle braking system. This is achieved by incorporation of extended surfaces over the compression face of the piston. The provision of extended surfaces over the compression face of the piston improves the heat extraction from the hot compressed air. The extracted heat is being carried away by the lubricant on the bottom side of the piston. This improved heat extraction reduces the delivery air temperature, thereby improving the cooling efficiency of the air compressor.

Full Text

The invention relates to air compressors and more especially it relates to a reciprocating air compressor. This invention in particular relates to piston with improved construction so as to improve cooling efficiency for air compressor in a motor vehicle brake system. Reciprocating compressors comprises a piston and cylinder arrangement with a cylinder head assembly over the cylinder. The cylinder head assembly is made of cylinder head, inlet valve and delivery valve and valve plate with inlet and delivery holes. The cylinder head has an inlet port opening to the inlet cavity and a delivery port opening into the delivery cavity. The inlet valve opens during induction stroke of the piston and the delivery valve opens during the delivery stroke of the piston. The air compressor intakes air at lower pressure through the inlet holes and compresses it to higher pressure and temperature through the delivery holes. The delivery cavity portion of the cylinder head is provided with extended surface for better heat extraction from the hot air. The heat extracted by the piston in tum carried away by the splash of the lubricating oil under the piston's top surface. Following are the undesired effects of high delivery air temperature in compressors of automotive air brake system 1. Increased carbon deposit formation from lubricating oil on valve plate surfaces and cylinder head. This will reduce the inlet and delivery valve life, 2. Increased oil consumption 3. Long metal piping for cooling the air in the system before entry into down stream units. Intake air in compressor is being heated up in the following ways. a. As the air travels into cylinder head inlet cavity and valve plate holes, it picks up heat from high temperature valve plate and cylinder head surfaces of inlet cavity. The heat transfer from valve plate and cylinder head surfaces to inlet air takes place by convection heat transfer. As the air travels further into the cylinder bore it picks up heat from high temperature cylinder bore and piston by convective heat transfer. b. As the air fills the cylinder bore during suction stroke, there will be heat flow from high temperature delivery cavity filled with hot air to air in cylinder bore through valve plate. The heat transfer from hot delivery air to valve plate takes place by convection. In valve plate heat transfer from top surface to bottom surface takes place by conduction. The heat transfer from valve plate surface to air in cylinder bore takes place by convection. c. During compression according to thermodynamic principles heat will be generated. The generated heat is a function of inlet air temperature, inlet air pressure and delivery air pressure and speed of compression. Heat extraction from hot delivery air can be accomplished by following ways. a. Extraction of heat from hot air to cylinder bore and piston surfaces by convective heat transfer. b. Conduction of heat from piston hot air contact surfaces to lubricating fluid contacting surfaces. c. Dissipation of heat from hot piston to lubricating fluid by convective heat transfer. d. Extraction of heat from hot air to cylinder head and valve plate surfaces by convective heat transfer. e. Conduction of heat from respective hot air contact surfaces to atmospheric air contacting surfaces. f. Dissipation of heat from hot cylinder head and valve plate to atmosphere by convective heat transfer in air cooled compressor. g. In water cooled compressor, dissipation of heat from hot cylinder head and valve plate to water coolant by convective heat transfer. Invention for better heat extraction from hot delivery air to cylinder head is claimed through another patent application 621/CHE/03 bearing the title "Cylinder head with improved cooling efficiency for air compressor for a motor vehicle braking system". The present invention is addressed at improving extraction of heat from hot piston to lubricating fluid by introducing extended surface area in piston. SUMMARY OF INVENTION The inventors have made great effort to provide a system, which will meet the requirement of the industry and overcome the problem associated in the prior art. To achieve the above object according to first aspect and feature of the present invention there is provided a system to improve cooling efficiency for air compressor for a motor vehicle braking system. According to second aspect and feature of the invention in addition to the first feature the invention comprises a system, which is unique, rugged, efficient and economical. At the outset of the description which follows it is to be understood that ensuring description only illustrate a particular embodiment of this invention. However, such particular embodiment is only an exemplary embodiment, and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and reading of the invention and not intended to be taken restrictively. Accordingly the salient feature of the present invention is by provision of extended surface over the crown of the piston. The provision of extended surface improves the heat extraction from the hot air and dissipation of heat to the lubricating system. According to the present invention, the piston is made up of aluminium casting machined to cylindrical component with circular grooves to accommodate piston rings. The compression face of the piston is provided with circular concentric extended surface for better heat extraction from the compressed hot air, which is the subject of the present invention. In conventional construction, the compression face of the piston will be a plain machined face without any extended surfaces for heat extraction. The conventional construction comparatively has a lesser capacity for heat extraction. Viston configuration for improved cooling efficiency for an air compressor in a motor vehicle braking system characterised by incorporation of extended surface over the compression face of the piston which improves the heat extraction from the hot air and conducting the heat to the bottom side of the piston and to the lubricating fluid by convective heat transfer thereby reducing the temperature of the air being compressed. The foregoing description outlined rather broadly preferred and alternative feature of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing and modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should realise such equivalent conception do not depart from the spirit and scope of the invention in its broadest form. The drawings are given by way of non-limitative example to explain the nature of the invention. The accompanying drawings are intended to provide further understanding of invention and are incorporated in and constitute a part of invention. The drawings illustrate an embodiment of invention and together with the description illustrate principle of invention. The drawings should not be taken as implying any necessary limitation on the essential scope of invention. The various features of the novelty, which characterise the invention, are pointed out particularly in the claims annexed to and forming part of disclosure. For a better understanding of invention, its operating advantages, and specific objects obtained by its use, reference should be made to the drawings and descriptive matter in which there are illustrated and described preferred embodiments of invention. Piston with improved cooling efficiency for air compressor in a motor vehicle braking system is characterised by incorporation of this specially designed piston. The said piston is linked to the crankshaft with connecting rod and gudgeon pin and being guided in the cylinder bore. During operation of the compressor, the rotary motion of the crankshaft is being converted to reciprocating motion of the piston thereby enabling the suction and compression strokes of the compressor. During the compression stroke of the compressor, extended surfaces of the piston on the compression face increases the heat dissipation from the hot air to the lubricant on the bottom side of the piston thereby the delivered air is at reduced temperature. Piston for improved cooling efficiency for an air compressor in a motor vehicle braking system characterised by incorporation of extended surfaces over the crown of the piston, whereby the heat extraction from the hot compressed air is enhanced by convective heat transfer. 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 baffle proposed herein. In the drawings, Figure 1 - illustrates the sectional view of the cylinder head and piston assembly of the air compressor with conventional piston. Figure 2 - illustrates the three dimensional view and sectional view of the conventional piston. Figure 3 - illustrates the three dimensional view and sectional view of the piston with square shaped extended surface. Figure 4 - illustrates the three dimensional view and sectional view of the piston with triangular shaped extended surface. Figure 5 - illustrates the sectional view of the cylinder head and piston assembly of the air compressor with extended surface over piston. Figure 1 The configuration of a conventional cylinder head and piston assembly is illustrated in figure 1. The cylinder head assembly consists of a cylinder head (1), valve plate (4), Inlet valve (12) and Delivery valve (13). The entire cylinder head assembly is mounted on the cylinder block (8), The delivery cavity of the cylinder head (1) consists of plurality of pin (14) like projections so as to increase the surface area of cooling. The valve plate (4) has two delivery passages (3) to allow the passage of compressed air from cylinder bore to delivery cavity. Further there is provided delivery valve (12) over the delivery passages (3). The piston assembly consists of a piston (5), three piston rings (6) and gudgeon pin (7). The piston assembly is assembled to the connecting rod (10) by inserting tne gudgeon pin(7) Into the bore of the connecting rod (10). The entire piston assembly slides into the bore of the cylinder block (8). The space above the piston (5) constitutes the compression chamber (11) and the space below the piston (5) constitutes the lubrication chamber (9). The compressor inducts the air during the induction process and compresses the air during the compression process inside the compression chamber (11). The heat generated during the compression process is being transferred to the walls of the cylinder block (8), valve plate (4) and to the piston (5). The rest of the heat is carried away with the delivered air. Heat transferred to the cylinder block ( 8), valve plate (4) and piston (5) should be maximised to reduce the temperature of the delivered air. In other words, lower the heat transfer results in problem of higher the temperature of the air being delivered. The very objective of the invention is to over come the problem associated with the prior art. The problem of lower heat transfer from hot compressed air to piston surface is addressed by incorporation of extended surface over the compression face of the piston. The configuration of the piston with extended surface is explained in detail in figure 3 and 4 of the drawings. Figure 2 This figure illustrates the construction of conventional piston used in air compressors. Conventional piston is a cylindrical component with a top compression face called crown (15). Three grooves (17) are provided along the cylindrical surface of the piston to accommodate the piston rings (6) shown in figure 1. Piston further has a locating bore (18) to accommodate the gudgeon pin. The lower portion of the piston below the gudgeon pin locating bore (18) is called as skirt (16). The piston on the bottom side (19) has a cavity to accommodate the connecting rod and for lubricating system to lubricate. In this conventional system, the heat generated during compression operation is being transferred to the crown (15) by convention process. Further the heat is conducted to the bottom side (19) of the piston and being carried away by the splash of lubricant by convention process. The conventional system does not aim at maximising the heat extraction from the hot compressed air through the piston crown resulting higher temperature of the hot air. Figure 3 This figure illustrates the innovative piston configuration with square shaped extended surfaces used in air compressors. The new construction is provided with extended surfaces (20) over the crown (15) of the piston. One way of providing extended surface is shown in figure 3 by providing plurality of concentric square shaped extended surface (20). This way of providing extended surface increases the surface area by thrice. Thereby heat extraction from the hot compressed air is increased. The extracted heat is being conducted to the bottom side of the piston and being carried away by the lubricant by convection process. As explained in the description, enhancement of the cooling efficiency is obtained by increasing the heat transfer from the hot compressed air to lubricant by providing extended surfaces over the crown of the piston. Figure 4 This figure illustrates the innovative piston configuration with triangular shaped extended surfaces used in air compressors. Another way of providing extended surface is by providing plurality of concentric triangular shaped extended surface (21). This way of providing extended surface increases the surface area. In a similar manner as explained in figure 3, the extraction of heat from hot compressed air is enhanced, there by improving the cooling efficiency of the compressor. Figure 5 This figure illustrates the sectional view of the cylinder head and piston assembly of the air compressor with extended surface over piston. In this construction, all the basic components of the conventional cylinder head and piston assembly as explained earlier in figure 1 other than the piston is retained. Only the conventional piston is being replace by innovative piston (5). This innovative piston (5) has plurality of extended surfaces (20) as explained in figure 3 and figure 4. This piston configuration as explained earlier results in better heat extraction from the hot air resulting in improved cooling efficiency of air compressor. It is understood that the invention has been explained in relation to specific embodiment. It is inferred that the foregoing description is only illustrative of the present invention and it is not intended that illustrative of the present invention and it is not intended that the invention be limited or restrictive thereto. Many other specific embodiments of the present invention will be apparent to one skilled in the art from the foregoing disclosure. All substitution, alterations and modification of the present invention, which come within the scope of the following claims, are to which the preset invention is readily susceptible without departing from the spirit of the invention. The scope of the invention should therefore be determined not with reference to the above description but should be determined not with reference to the above description but should be determined with reference to appended claims along with full scope of equivalent to which such claims area entitled. We claim: 1. Piston for improved cxioiing efficiency for an air compressor in a motor vehicle braking system characterised by incorporation of extended surfaces over the crown of the piston, whereby the heat extraction from the hot compressed air is enhanced by convective heat transfer. 2. Piston for improved cooling efficiency for an air compressor in a motor vehicle braking system as claimed in claim 1, wherein the extended surface in the form of serration over the crown of the piston. 3. Piston with improved cooling efficiency for air compressor as claimed in claim 1, wherein the extended surface is in the form of square shape configuration. 4. Piston with improved cooling efficiency for air compressor as claimed in claim 1, wherein the extended surface is in the fonm of triangular shape configuration. Dated this the 26th day of March 2004

Documents:

0275-che-2004-abstract.pdf

0275-che-2004-claims.pdf

0275-che-2004-correspondnece-others.pdf

0275-che-2004-description(complete).pdf

0275-che-2004-drawings.pdf

0275-che-2004-form 1.pdf

275-che-2004 amended pages of specification 26-07-2011.pdf

275-che-2004 amended claims 26-07-2011.pdf

275-che-2004 amended pages of specification 26-07-2011.pdf

275-CHE-2004 CORRESPONDENCE . OTHERS 26-07-2011.pdf

275-che-2004 form-1 26-07-2011.pdf

275-CHE-2004 AMENDED PAGES OF SPECIFICATION 21-02-2011.pdf

275-CHE-2004 AMENDED CLAIMS 21-02-2011.pdf

275-CHE-2004 CORRESPONDENCE OTHERS 26-07-2011.pdf

275-CHE-2004 CORRESPONDENCE OTHERS. 18-10-2011.pdf

275-CHE-2004 EXAMINATION REPORT REPLY RECEIVED 21-02-2011.tif

275-CHE-2004 FORM-13 18-10-2011.pdf

275-CHE-2004 FORM-13-1 18-10-2011.pdf

275-CHE-2004 FORM-6 17-04-2008.pdf

275-CHE-2004 POWER OF ATTORNEY 26-07-2011.pdf

275-CHE-2004 AMENDED PAGES OF SPECIFICATION 18-10-2011.pdf

275-CHE-2004 AMENDED CLAIMS 18-10-2011.pdf

275-CHE-2004 CORRESPONDENCE OTHERS 18-10-2011.pdf

275-CHE-2004 FORM-1 18-10-2011.pdf

275-CHE-2004 FORM-18 29-06-2007.pdf

275-che-2004-form 13.pdf