Title of Invention	VALVE REEDS AND APPARATUS AND METHOD FOR MAKiNG THE SAME
Abstract	A method of manufacturing a valve reed comprising the process steps of a. Blanking from raw material, b. Deburring and edge Raduising step, c. Compressive stress induction step carried out by applying gravitational force of 8 to 10G, typically by an oscillating spindle, d. Polishing step for improving surface finish.

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FORM 2 THE PATENT ACT 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) A METHOD OF MANUFACTURING VALVE REEDS HAVING COMPRESSED STRESSES INDUCED THEREIN GALA PRECISION TECHNOLOGY LIMITED an Indian Company of 116, Narayan Dhiiru Street, Mumbai 400 003, Mahaarashtra. India This invention relates to Valve Reeds for Hermetic and Semi-Hermetic Compressors. In particular this invention envisages a method of manufacturing and a method of inducing high compressive-residual stress in Valve Reeds. This invention particularly relates to Valve Reeds manufactured from Flapper Steel and by a novel method and apparatus for making the same. Background Compressive stress induction is one of the important process steps for components working under dynamic conditions. The number of cycles performed by a particular component defines life of the component such as Turbine blades of engines, Compressor Valves, Blades, Springs, Connecting Rods, Gears, and the like . During manufacturing, these components undergo various operations like Blanking, Machining, Bending etc. During these processes tensile stresses are developed in the components. If compressive stresses are not induced in the component the life of component will be much lower then it is designed for. Compressive Stress Induction in Valve Reeds The thickness of Valve Reeds used in compressor varies from 0.152mm to 1.00-mm. Surface finish requirement for these Valve Reeds is normally specified by compressor manufacturers. A very high surface finish [Ra] (between 0.05microns to 0.20 microns) is required for Valve Reeds required for use in compressors. Fatigue of Strain Hardened Machine Components In many types of service applications metal components such as valve reeds, are subjected to repetitive or cyclic stresses. They will fail at a much lower stress than a component which is only subjected to a single static stress. Failures which occur under repeated or cyclic stressing are called fatigue failures. One of the most effective methods of increasing fatigue performance is by inducing residual compressive stresses within a thin outer surface layer of the component. A surface tensile stress of external origin applied to the component will be partially nullified and reduced in magnitude by the residual compressive stress. The net effect is that there is less likelihood of crack formation and therefore the fatigue failure is reduced . Also the cycles to failure depend strongly on the type of surface treatment applied so that in shot peening treatment they range between 200.000 and 800.000 cycles for failure. This invention particularly relates to a an improved valve reed and a novel process of inducing compressive stresses in valve reeds in accordance with this invention . Conventional Process/ method for manufacture of Valve Reeds involve the following steps: 1) Blanking from Raw Material 2) Deburring & Edge Raduising process 3) Polishing for Improving Surface Finish process The process in accordance with this invention involves the following novel steps involved in the manufacture of valve reeds : 1) Blanking from Raw Material 2) Deburring & Edge Raduising process 3) Compressive Stress Induction step 4) Polishing for Improving Surface Finish process The blanking from raw material is carried out by conventional manner by a blanking machine. The Deburring & Edge Raduising processes are done by a conventional method carried out in a tumbling barrel and involves the following procedure: Components (Valve Reeds) after blanking are loaded in tumbling barrel with different types of abrasive stones of irregular shape & size and water. Some manufacturers also use abrasive powders to increase the cutting action. Cycle time varies from 20 hours to 70 hours per batch depending on the type of Reeds, thickness of raw material and type of finish required. Shot peening is the traditional and proven method for induction of Compressive-residual Stress in components. Shot peening is a process of mechanical hardening of the surface layers of machine components applied in order to ensure compressive residual stresses induced on the surface layer to improve the fatigue strength / life of a material, resistance to fretting, and stress-corrosion resistance. Shot peening is a process in which a component is bombarded with tiny balls of steel, cut-wire, Glass or ceramic shot. In the assessment of the quality of the shot-peened layer, the highest value of the compressive stress at the surface or just below it and the gradient of compressive stress are of major importance. For a comparison of results two shot velocities, i.e. vl = 25 m/s and v2 = 40 m/s, and two mass flow rates, i.e. 1 = 200 g/min and 2 = 600 g/min, were chosen. Residual stresses were measured always in the centre of the specimens using standard X-ray diffraction methods. Radiation was used to measure lattice strain distributions at {211}-lattice planes of Ferrite or Martensite respectively. The area irradiated by the X-ray beam was collimated to a diameter of 1,0 mm. For the calculation of residual stress values from the measured lattice strain distributions, the elastic constants E = 210 MPa and Poisson's ratio = 0.285 were used. Depth distributions of residual stresses were determined by successive electrochemical layer removal. Characteristic data on the residual stress variations permit very important findings, i.e., after hardening by shot peening relatively high compression stresses can be achieved and the process provides favorable stress gradients in the greater depths of the subsurface. Advantages of Shot Blasting Process for Compressive Induction: • High Level of compressive stress induction, resulting in higher fatigue life. • Enhances lubricity by creating small pores • Creates a uniform texture. • Improves coating adhesion. • Can permit the use of very hard steel by reducing brittleness. • Will close up surface porosity. Disadvantages of Shot Blasting Process: A) As mentioned above this process is done by bombarding shots of Steel or Wire or Glass, on surfaces of components dent marks are left, making surface rough & distortion in Surface Finish ( Ra Value). This process is therefore not found suitable for 1) Components requiring high level of surface finish ( Ra Value below 0.20 Micron) 2) Thin ( Thickness below 0.8 mm) & fragile components ( Get distorted due to very high pressure of shots) 3) Shot blasting machines are self-destructive machines as cost of maintenance is very high due to lot of pressure shots requires for blasting. Considering the limitation of shot blasting process, Compressor Valve Reeds cannot be treated for compressive stress induction as defined in prior art by conventional methods such as shot peening . Therefore it was hitherto not possible to induce compressive stresses in valve reeds Therefore there was need for another method for inducing high level of compressive stresses in Valve Reeds for higher fatigue life of Reeds. The novel inventive feature of this invention is the induction of Compressive Stress in Valve Reeds. The compressive steps induction in Valve Reeds involve following process step: The process is done in a Machine by which the individual valve reeds are subjected to Gravitational (G) forces typically in the range of 7 to 10 G. These G forces can be applied by providing the valve reeds with angular displacement such as in the form of a displacing or an oscillating pendulum on or within which the valve reeds may be held by fixtures specially designed to hold the reeds while they are being angularly displaced. Obviously, the shape and size of these fixtures will depend upon the size and geometry of the valve reeds. Media may advantageously be used for this process during the stress inducing process. Media is added to act as a coolant during process. These include carbides, polyester or silica based compounds. The cycle time for this process varies from 2 to 4 hours per batch depending on the type of Reeds, thickness of raw material. As a result of this process high level of compressive stresses are induced in the Valve Reeds with greater depth of penetration. This results in higher fatigue life of Valve Reeds. According to present invention a gravitational force typically of 8 G is applied on Valve Reeds to induce high compressive stress. A typical machine used for finishing of these Valve Reeds is a machine having a spindle generating oscillations at speed of 200 oscillations per minute to 940 oscillations depending on shape, size, thickness & quantity of Reeds to be processed. The amount of force generated during the processing is 220 KN. The cycle time for stress induction varies from 2 hours to 4 hours depending on thickness of Reeds & area of component on which stress is to be induced. For example the residual (compressive) stress level was between 180 to 210 MPa before processing in a spindle type machine G forces inducing machine & after finishing the compressive stress induction level was found between 380 to 425Mpa. Media is used which among other things acts as a coolant. This media is manufactured from hard polyester with Silica, Carbide. The advantage of using polyester is its low bulk density, ensures that no dent marks are left on surfaces of Reeds The Moh hardness of these media vary from 4 to 7. By processing Reeds in this method, high level of compressive stresses (residual Stresses) are induced resulting in High fatigue life of Reeds. The surface finish of Reeds by this process is achieved in the required range of 0.05 to 0.20 microns, which is not possible to achieve by blasting process. Also there is NO distortion to the component in terms of Shape, flatness & parallelism. Flatness & parallelism are achieved in required limits of 0.08 to 0.30 mm. Example 100 Valve reeds were mounted on fixtures. The design of fixture was based on shape of Valve reed , thickness of valve reed material, Critical profiles of Valve reed . After loading the reeds in the fixtures, [100 Fixtures were selected ] (depending on shape of reed) the reeds were placed in a spindle container. The spindle was given Oscillatory movement at the rate of 750 oscillations per minute for 100 minutes. The spindle was pre loaded with media in the form of polyester beads of 4 mm diameter. During this movement / process forces of 8 G were generated resulting in induction of high level of compressive stresses in Valve reeds ( 400 MPa). Most important fact is that induction level of residual / compressive stresses is much higher as compared to shot blasting operation or any other method like of conventional tumbling. This is confirmed by theoretical measurement of residual stresses done by X ray Stress Analyzer AST X2001 at National Metallurgical laboratory in Jamshedpur, in India as illustrated in test data provided in Example 2. Valve reeds in which stresses were induced in accordance with this invention were tested and compared with conventionally manufactured valve reeds The test data is illustrated in Example 1. Table 1 and II of example 3 shows the results of test. The results shows fatigue test of Valve Reeds & Comparing 2 Reeds of same design on a fixture. A comparison test of the Reeds in accordance with this invention and those in the prior art is found in table 1 of example 3 which confirms that the Reeds in accordance with this invention have strong residual stresses. END RESULT: Stronger compressive stresses results in higher fatigue life of Valve Reeds The Reeds in accordance with this invention were compared with their existing Reeds for different cycles at different deflections and different frequencies (Hz). The results are tabulated in example 1 to 4. Another aspect of the invention is the novel polishing for Improving surface finish step in accordance with this invention. Conventional Method for Polishing for improving surface finish: The process uses the same tumbling barrel with other or same grade of abrasive media. Compounds used by them are basically soaping agents with high foam resulting very gentle motion between Reeds & abrasive stones. End result is improvement in Surface finish. Cycle time per batch varies from 2 to 7 hours per batch depending on the type of Reeds, thickness of raw material and type of finish required. The surface finish (Ra Value ) achieved by this method is between 0.08 microns to 0.22 microns depending on the type of Reeds, thickness of raw material. The various test to know the improved property of valve reeds manufactured by present invention were conducted at different laboratories. It is illustrated in the results tabulated and compared in the examples and table below. Example 1 Residual Stress measurement by Comparing Reeds manufactured in accordance with this invention [Gala] with Reeds produced conventionally [conv] (compressive stress induced by Shot peening method). Compressive Residual surface stress measurement in Mpa, by X-ray diffraction using Cr-Ka. Example 2 Comparison report between different types of Reeds manufactured by Gala with Reeds manufactured conventionally [conv]. END RESULT: Stronger compressive stresses results in higher fatigue life of Valve Reeds Example 3 Table I Results of tests conducted at Comparing Gala Reeds with conventional reeds. Results of Fatigue Tests at 3.0 Hz Example 3 Table II Results of Fatigue Tests at 3.3 Hz Example 4 Comparison done between compressive stress induction for Valve Reeds before & after finishing: As Valve Reeds have top perform under dynamic working conditions inside the compressor, the running life / fatigue life of Suction & discharge Valve Reeds plays critical role. The process of manufacturing Valve Reeds by the present inventive method is different than the other Reeds manufacturer. The process by present invention induces higher level of compressive stresses compared to conventional methods like shot blasting. Various studies and comparative analysis done on Valve Reeds manufactured by this process and compressor manufacturers, metallurgical laboratories and steel manufacture support the claim. 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. We Claim: 1. A method of manufacturing a valve reed comprising the process steps of a. Blanking from raw material, b. Deburring and edge Raduising step, c. Compressive stress induction step carried out by applying gravitational force of 8 to 10G, typically by an oscillating spindle, d. Polishing step for improving surface finish. 2. A method of manufacturing as claimed in claim 1 in which the gravitational force is achieved by a spindle moving at a speed of 200 to 400 oscillations per minute to carry out said Compressive Stress Induction process. 3. A method of manufacturing as claimed in claim 1 wherein the force generated during the said Compressive Stress Induction process is 220KN. 4. A method of manufacturing as claimed in claim 1 wherein the cycle time per batch for said Compressive Stress Induction process is 2 to 4 hours. 5. A method of manufacturing as claimed in claim 1 wherein the said Compressive Stress Induction step induces compressive stress in the range of 380 to 425 mpa. 6. A method of manufacturing as claimed in claim 1 wherein the said Valve Reeds along-with media loaded in proportion in an apparatus in which the Gravitational forces are applied. 7. A method of manufacturing as claimed in claim 6 wherein the said media comprises media selected from Polyester , Silica, and Carbide. 8. A method of manufacturing as claimed in claim 7 wherein the said media has Moh hardness in the range of 4 to 7. 9. A method of manufacturing Valve Reeds as substantially as herein before described and explained with reference to the examples. Dated this 1st day of June 2005

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261-mum-2004-cancelled pages(3-4-2006).pdf

261-mum-2004-claims(granted)-(3-4-2006).doc

261-mum-2004-claims(granted)-(3-4-2006).pdf

261-mum-2004-correspondence(3-4-2006).pdf

261-mum-2004-correspondence(ipo)-(16-4-2007).pdf

261-mum-2004-form 1(3-3-2004).pdf

261-mum-2004-form 13(21-6-2005).pdf

261-mum-2004-form 18(29-8-2005).pdf

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261-mum-2004-form 2(granted)-(3-4-2006).pdf

261-mum-2004-form 26(3-3-2004).pdf

261-mum-2004-form 3(3-3-2004).pdf

261-mum-2004-form 4(30-12-2004).pdf

261-mum-2004-form 5(1-12-2005).pdf

261-mum-2004-form 5(1-6-2005).pdf

261-mum-2004-form 9(6-6-2005).pdf