Title of Invention

COLD FORWARD EXTRUSION WITH ENHANCED REDUCTION RATIO IN SINGLE STAGE

Abstract

A cold forward extrusion tool comprising: a die assembly having a die stopper and a die/preform chamber for placing a preform to be extruded, housed in die housing and die assembly; a punch assembly having a punch head and a stopper adapted above the die assembly for extruding a preform; a reciprocating ram connected to the punch assembly enabling to reciprocate the punch assembly to move in vertical direction wherein said stoppers control the vertical movement of the punch assembly thereby controlling the head thickness of extruded component obtained by punching the perform and obtaining higher reduction ratio in single step with the help of die chamber, die housing and die assembly.

Full Text

FORM 2 ORIGINAL 425/MUMNP/2003 THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See section 10, Rule 13] COLD FORWARD EXTRUSION WITH ENHANCED REDUCTION RATIO IN SINGLE STAGE; LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT S TO BE PERFORMED. GRANTED 22-5-2006 TITLE "COLD FORWARD EXTRUSION WITH ENHANCED REDUCTION RATION IN SINGLE STAGE" TECHNICAL FIELD Present invention related to manufacture of components having extremely complex configuration and manufacturability and requiring high level of precision and very close tolerance especially for components used in the manufacture of electrical and/or electronic goods. This invention is aimed at developing a novel tool and process for manufacturing such components and this has been achieved by developing a complex tool, which uses the novel process of cold forward extrusion with enhanced reduction ration to manufacture such components in single stage. PRIOR ART Hot Forging is a commonly used process for manufacturing components of above description. According to conventional methods, hot forging is carried out at very high temperature. However, is suffers from various drawbacks such as poor material utilization higher power consumption and large dimensional deviation. Also it leads to poor accuracy and the component produced has poor surface finishing, hence, secondary machining operation is necessary. This process also leads to inferior electrical conductivity; oxidation and scaling may further affect the performance of the component. Upsetting is another process conventionally employed for manufacturing such components, especially inner plated of fuses. The drawback of this particular method is that is requires raw material of special shape. This may be costly to obtain and leads to poor dimensional consistency. Also, the process requires extra machining to control dimensions. Brazing, as conventionally used, is a process in which two separate components say, in the case of inner plates fuses, the head and the knife are produced separately and are joined together. Since two components are produced separately and joined later, this process is costly. Also, it requires secondary machining operation to remove excess brazed material. The strength of the joint is also poor and hence difficult to use for mass production. Most importantly, however the main disadvantage lies in the fact that is consumes more power because of its high electrical resistance. The process of hot extrusion as conventionally used is carries out at very high temperatures. It can have one or two stages depending upon the reduction ration to be achieved. However, only upto 50%-55% reduction ration can be achieved in a single stage of hot extrusion for copper, brass, aluminum and steel. In order to achieve a higher reduction ration, the hot extrusion has be carried out in two stages. Another disadvantages of this method is that it needs special arrangement for heating the preform and handling them in hot condition. The stress developed during conventional single stage extrusion is so high; the strength of the tool would be critical. Double stage hot extrusion, is used for reduction, but has a drawbacks of leaving a small corrugation or step on the functional surface of the component, Hence, it too, needs a secondary machining operation. The process has poor accuracy, and the tool life is also poor, more over, ejection of the component is very difficult. Its performance is liable to be degraded due to oxidation or scaling and the power consumption of the resultant component is high. Because of all the aforesaid drawbacks of the conventional methods, these are not suitable for manufacturing components having a complex configuration and manufacturability. We have invented a novel tool, which employs and entirely new process for the manufacture of such components. The advantage of our invention is that components having very high accuracy can be developed using this tool. The resultant components have no or very marginal dimensional deviation. Another advantage of our invention is that the components produced have a very good surface finish and hence, there is no need for secondary machining operation. The tool is requires to withstand very high stresses, and hence it is very high strength. It is extremely economical because it makes optimum material utilization and there is no material loss. The tool has high speed; and hence, is suitable for producing components voluminously. Complex shapes of components can be extruded using this tool. More importantly, our novel invention ensures that the components produced have good electrical conduction and low wattage loss. Close tolerance is achieved in this process of cold extrusion employed by the tool. The components produced consume less power than the components produced by the above-mentioned conventional processes. DISCLOSURES OF THE INVENTION. The present invention 'Cold Forward Extrusion with Enhanced reduction ration in single stage" is designated to eliminate all the drawbacks of conventional methods in large-scale manufacture of complex components! One of the objectives of the present invention is to develop a tool, which is very accurate and has the ability to extrude components having complex shapes accurately. The tool should be able to provide very high reduction ration in single stage. For this is should be able to withstand high stress, and therefore should have very high strength. Also the extruded component should have negligible dimensional deviation. Yet another objective of this invention is to develop a tool, which will employ a process having 100% material utilization, and provide in-built auto-ejection mechanism. Also, the objective is to develop a tool with high speed so as to make it suitable for mass production and to ensure that the components extruded same good electrical condition and low wattage loss. The present invention of cold forward extrusion with enhanced reduction ration in single stage was developed successfully after carrying out extensive research and trials and achieves all the objectives as mentioned above. Forward extrusion is a process in which the work metal or preform is forced in the direction of the punch travel. The newly invented tool uses a process 'cold extrusion', which is used herein to relate to a process in which preform enters the tool at room temperature. The tool employing the novel "cold forward extrusion" is constructed using special tool steel and a special manufacturing process. Special tool steel is required to withstand very high stresses developed due to very high percentage reduction ratio. Hence, the die is designed to have very high strength. The assembly mainly consists of two-parts-a punch and a die. A die chamber is provided in the die assembly to place the preform. A die stopper is made to control the relative movement of punch assembly. The tool is embedded with an auto ejector mechanism, which removed a component once it is extruded. The punch applies pressure to the preform in die chamber. Another die stopper is provided on punch assembly, which helps the stopper in die assembly to control the vertical movement of punch assembly. The die assembly is fixed to a stationery bed and the punch assembly is attached to a reciprocating ram. A copper preform having requisite dimensions is placed in the die chamber. The punch assembly then descends and rapidly applied very high force on the preform. Because of this sharp blow of pressure, the material has no scope, but to flow in the direction of punch movement. A pair of die stoppers controls this movement of punch assembly. The movement of die stoppers determines head thickness of the component. Finally, in upward movement of the ram of the press, an auto ejector mechanism removes the component out of the die and an operator can take out the extruded component. The cold forward extrusion method is a single stage method, because the required shape of the component is achieved in a single stroke. Percentage reduction ratio: Percentage reduction ration determined by using the following formula Percentage reduction = ((A0-A1)/A0)*100 Where, Ao = Area of head of the extruded component (3) A1 = Area of knife of the extruded component (4) As illustrated in sketch 2(b) The development process mainly included following steps. i) Many prototypes of tool were designed, manufactured and trials were carried out. ii) When trials were successful, a suitable lubricant was identified. iii) Thereafter, die construction was thoroughly checked for withstanding very high and complex stresses, iv) Since the invention has to be developed for mass production, selection of appropriate material and hardness of tooling elements was carried out. v) Finally, inbuilt arrangement for ejection of the component was incorporated in the tool. BRIEF DESCRIPTION OF DRAWINGS Figure 1a illustrates the top view of preferred embodiment of the preform. Figure 1b illustrates elevation of the preferred embodiment of the preform. Figure 2a illustrates elevation and top view of the extruded component. Figure 2b illustrates the side view of the extruded components. Figure 3 illustrates the preferred embodiment of the cold forward extrusion tool. Figure 4 illustrates a flow diagram of the cold forward extrusion process. DESCRIPTION OF PREFERRED EMBODIMENT The invention will now be described in greater detail with the reference of accompanying drawings. In its preferred embodiment, the preform (figure 1a) is a copper preform. In its preferred embodiment, the extruded component (figure 2b) is the inner plate of a fuse. As shown in figure 3, the preferred embodiment of the cold forward extrusion tool has a vertical axis. It is constructed using special steel and special manufacturing process. The assembly mainly consists of two parts punch (5) and a die (7). In its preferred embodiment, a die chamber (6) is provided in the die assembly (7) to place the preform. A die stopper (9) is made to control the relative movement of punch assembly item no. (8) Is an auto ejector mechanism. It is used remove a component once it is extruded. In the punch assembly, item no. (5) is a punch head, which applies pressure to the preform in die chamber (6). Another die stopper (9) us provided on punch assembly, which helps the stopper in doe assembly to control the vertical of movement of punch assembly. The assembly is fixed to stationery bed and the punch assembly is attached to a reciprocating ram. Description of cold forward extrusion process: - Please refer to the flow diagram of cold forward extrusion process as given in sketch 4. In the preferred embodiment a copper preform as shown in figure 1 is placed in the die chamber (6) as shown in step 1. The punch assembly then descends and rapidly applies very high force on the preform (step 2). Because of this sharp blow of pressure, the material has no scope, but to flow in the direction of punch movement (Step 3). A pair of die stoppers (9) controls this movement of punch assembly. Head thickness of the component as shown in figure 2a & b is taken out by an operator (Step 6). The desired component is achieved in a single stage. Percentage reduction ratio: - Extrusion ratio or percentage ratio is determined by the below mentioned formula Percentage Reduction = ((A0-A1)/A0)*100 Where, Ao = Area of head of the extruded component (3) A1 = Area of knife of the extruded component (4) As illustrated in sketch 2b The enhanced ratio is maintained in this process of cold forward extrusion. While the invention has been described with reference to the preferred embodiments, those skilled in the art will understand that various changes my be made and equivalent may be substituted for elements thereof without departing form the scope of the invention. In addition, many modifications may be made to adopt the particular situation or materials to the teachings of the Invention without departing from the essential scope thereof. Therefore it is intended not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but the invention will include all the embodiments falling within the scope of the appended claims. WE CLAIM: 1.) A cold forward extrusion tool comprising: a die assembly having a die stopper and a die/preform chamber for placing a preform to be extruded, housed in die housing and die assembly; a punch assembly having a punch head and a stopper adapted above the die assembly for extruding a preform; a reciprocating ram connected to the punch assembly enabling to reciprocate the punch assembly to move in vertical direction wherein said stoppers control the vertical movement of the punch assembly thereby controlling the head thickness of extruded component obtained by punching the perform and obtaining higher reduction ratio in single step with the help of die chamber, die housing and die assembly. 2.) A tool as claimed in claim 1 wherein the said die assembly optionally comprises a conventional auto-ejector mechanism. 3.) A tool as claimed in claim 1 or 2 wherein said die and punch assembly constructed using special steel to withstand very high stresses resulting due to such a high percentage reduction ratio. 4.) A tool as claimed in claim 1 or 2 wherein material of said preform is copper or any other extrudable material. Dated this 28thday ofApril2003

Documents:

425-mum-2003-cancelled pages(22-05-2006).pdf

425-mum-2003-claims(granted)-(22-05-2006).doc

425-mum-2003-claims(granted)-(22-05-2006).pdf

425-mum-2003-correspondence(ipo)-(08-11-2006).pdf

425-mum-2003-correspondence1(12-06-2003).pdf

425-mum-2003-correspondence2(15-11-2006).pdf

425-mum-2003-drawing(22-05-2006).pdf

425-mum-2003-form 1(22-05-2006).pdf

425-mum-2003-form 1(29-04-2003).pdf

425-mum-2003-form 13(18-01-2005).pdf

425-mum-2003-form 18(06-07-2005).pdf

425-mum-2003-form 2(granted)-(22-05-2006).doc

425-mum-2003-form 2(granted)-(22-05-2006).pdf

425-mum-2003-form 3(05-11-2003).pdf

425-mum-2003-form 3(22-05-2006).pdf

425-mum-2003-power of attorney(18-01-2005).pdf

425-mum-2003-power of attorney(21-03-2003).pdf

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