Title of Invention

IMPROVED STUD/BOLT HEATER, ELECTRICALLY OPERATED

Abstract

An improved stud/bolt heater with carbon/graphite resistance (09) as heating element push fitted, at one end in axial blind hole in a plug (10) being welded to the upper pipe (11) encasing the total resistance assembly, the resistance (09) being electrically insulated from pipe (11) by insulating porcelain sleeve (07) other end of the resistance (09) being electrically connected to a top plug (08), which is electrically connected to a lead (06) connected to connecting strip (03), fastened to it by a threaded nut (05a) & check nut (05) the connecting strip supported on the main supporting "L" bracket (04) by insulated joint and further extending from an electrical supply connection, "L" bracket (04) being provided with bolt (16a), nut (17a) and washer (18a), the link strip (12), having connecting terminal formed by bolt (16), nut (17) and washer (18), the link strip (12) being provided for proper electrical contact the cover fixed with cheese head screw to the "L" bracket to support porcelain insulator (02) provided with a spring guide (26) and a spring (25) guided in it so as to retain the resistance assembly in pipe but to allow for the thermal expansion of the said resistance assembly and keeping it insulated it in case the assembly expands/ elongated thermally to reach the part of the cover (01) above it, by means of the porcelain insulator (02), the other electrical supply connections being formed on "L" bracket (04), the porcelain insulator (02) affixed to cover (01) by rivet (20) : the said pipe (11) provided with a axially slidable bush (22) on its outer diameter, the bush being with a locking screw (21).

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION [See section 10] IMPROVED STUD / BOLT HEATER, ELECTRICALLY OPERATED; BABUBHAI KANTILAL DOSHI AN INDIAN NATIONAL OF 623-1, GIDC INDUSTRIAL ESTATE, ANKLESHWAR 393 002, IN THE STATE OF GUJARAT, WITHIN THE UNION OF INDIA; THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFOMED. , ., 25-8-2006 This invention relates to the improved stud/bolt heater, electrically operated. The stud/bolt heaters are mainly used as an assembly tool for heavy machinery like turbines, where precise prestressing of the fasteners like stud/bolts is a prime requirement .Without prestressing , the fasteners can come loose during working conditions due to differential thermal expansion and pressure, thus disturbing the normal function of the machine. The turbines are high speed rotary machines and they operate at high temperatures. Due to this, the material specification and dimensional precision i.e. the relative positions of the working parts is of utmost importance through out the working time .More over the turbines form a very expensive part of the electrical power generation plants, thus interruption of the working due to any kind of malfunction can lead to losses which are not only the large revenue losses of the generating plant, but have impact on the national productivity. Considering this the stud/bolts of the turbine are tightened or loosened for maintenance using specific methods recommended by the turbine manufacturer. The manufacturers of the turbines use hollow studs/bolts for the assembly .During assembly these studs /bolts are first tightened in the traditional manner by using spanner/ wrench. Thereafter these studs/bolts are heated by inserting the stud /bolts heater in the 2. hollow of these stud/bolts The stud/bolt heater heats the stud/bolt by electric resistance heating process. The stud/bolt thus heated/elongates due to thermal expansion of the same and hence loosens as the fastened parts do not expand to same extent due to being at lower temperature than the stud/bolt . The stud/bolts are further tightened in this condition to the precise requirement as recommended by the turbine manufacturer. The heater is then withdrawn and as stud/bolts cool down they shrink to their size at the ambient temperature. This causes further tightening of the studs/bolts with required precision and uniformity of tightness. With this the possibility of them getting disturbed during running is eliminated. Various type of stud/bolt heater are used depending on the design of the turbines. Presently the standard type of studs/bolts heater used are of electrically heated type, they use electrical resistance wire for heating purposes. During heating of the stud/bolts the time period of heating is very important, The heating should be as fast as possible. There should be minimum possible heat flow to the turbine body, so as to keep high temperature difference between turbine body and stud/bolts to achieve the differential thermal expansion required for the tightening of the stud/bolts The shorter the heating up time , the lower Is the heat conducted . For this, the heaters are manufactured with very high heating load per unit area of the heater, popularly expressed in watts/cm2 . With advent of new compact designs in turbine industry 3 the demand for higher surface, heat loading of these heaters is increasing. This means the heaters should be of higher wattage and further compact in size. The traditional stud/bolts heaters are falling short of this demand, to the extent that the requirement of high watt density in small size has become impossible to be met with. For the sake of longer life and safety it is recommended to use lowest possible voltage for stud/bolts heaters. The traditional stud/bolts heater are designed to work with 230V supply. This makes it unsafe for use, as it calls for giving very high watt density heaters, working at an unsafe voltage ,in the hands of moderately qualified users. The improved studs/bolt heater overcomes all these inadequacies. The improved studs/bolts heater makes use of properties of carbon/ graphite for electrical heating. Carbon/graphite having low electrical resistance can withstand the temperature up to 2500degree C. This can give very high watt density even with low supply voltage of @ 24V which is entirely safe for use. DESCRIPTION: The improved stud bolt is described be; low with reference to the drawing(s) as follows: Fig.1 Shows the improved stud/bolt heater in its elevaton. Fig.2 Shows the sectioned view of the stud/bolt heater along the section line A.A shown in Fig: 1. Fig 3 Shows the top view of the stud bolt heater. 4 The top cover (01) is a cover formed of sheet metal to cover the electrical assembly of the stud/bolt heater, keeping the terminal connection open for wiring .A porcelain insulator (02) is affixed to top over (01) by means of rivet (20). The 'L" bracket (4) is made of heavy gage metallic sheet. The 'L' bracket (4) has three holes provided in it for electrical connections two holes being at one end while one at other end, through which the end of the pipe (11) is inserted & the pipe welded to the L bracket so as to project whole length of pipe(11) &N2y from the side of the top cover (01). The pipe (11) is made of a corrosion resistant metal like suitable stainless steel. On the outer side the pipe is provided with a bush (22) is, which can slide over the pipe. The bush has a stepped outer diameter. For providing the location diameter for the pipe, while the collar formed by step can be used as a stopper on insertion of the pipe in the hollow of the stud/bolt. The bush (22) is provided with a threaded hole in radial direction on the bigger diameter of the stepped profile, through which is fitted a cheese head screw (21) to provide locking at desired location in the lengthwise direction on the pipe (11), by tightening the said cheese head screw. The pipe (11) is provided with a plug (10) which is inserted at the outer end of the pipe & welded in place with the pipe(11). . The plug (10) is provided with a blind hole facing the inner side of the pipe. One end of carbon /graphite resistance (09), which forms the heating element of the stud/bolt heater, is push fitted in the hole provided in the plug (10), while the other end is similarly push fitted in an axially drilled blind hole, in top plug (08) provided at the other end of the resistor (09) .the top plug (08) is in turn having 5 another axially drilled bilind hole at the other end which engages with the lead (06) which has a male counterpart to be push fit in the axial hole of top plug (08).The lead (06) fits near the inner end of the pipe (11) and is insulated from the pipe by an insulting sleeve (07) made of procleain. The lead (06) is provided with a collar and a threaded portion at the inner end on to which connecting strip (03) is affixed with nuts (05A) and check nut (05). The said porcelain insulator (02) fixed in cover (01) is axially in line with the pipe (11). Incase of thermal expansion of the assembly inside the pipe, which can extend towards the cover (01) in extreme case the nut (05) can touch the insulator (02) and the not the metallic part which could have caused a short circuit. The insulator (02) has female step at bottom end as spring guide (26) which guides the retaining spring (25) which keeps the resistance assembly pushed inside the pipe (11), at the same time does not obstruct the thermal expansion of the same. All the parts which carry electric current and also get heated viz. lead (06),top plug (08) & plug (09) are also required to maintain their physical strength & dimensional stability, are made up of refactory metals, tungsten, molybdenum and the like . These parts reach upto about 1500 degree c temperature during working. The connecting strip (03) is made up of electrically conducting material like copper and is formed in multiple "U" bends to allow minimum amount of heat to reach the other end and also to impart it flexibility to the same. Strip (03) is provided two holes which are used for fixing and connecting the electrical supply to the same. A link strip (12) with bolt (16), nut (17) and washer (18) are a fixed at the hole at the farthest 6 end, all these parts being made of brass. The other hole of link strip (12) is matched with that of connecting strip (03) and "L" bracket (04) and bolt (15) is passjdjthroyg]i.wJth jnsulating spacer(13) in position and fastened with nut (17b)yand washe/ (18b) With this the reconnecting strip (03) is supported on "L" bracket (04) rigidly but with tfi, electrical insulation. 7 The link strip (12) ensures proper electrical contact between supply and lead (6) and is made of copper. Another hole is provided on "L" bracket (04) shifted laterally, from the section line A.A in Fig.1 .A bolt (16a), nut (17a) and washer (18a) form an electrical terminal where the electrical supply cable or its lug can be fastened. Bottom portion of the top cover is given a "U" shape at the portion overlapping the joining bolt (15) to cover protect and this electrical contact: this shape is shown as (14) in fig 1 and Fig 2. The top cover (01) is affixed to "L" bracket (04) by cheese head screws (19) .A label plate (23) indicating the voltage current rating etc, is fixed to the top cover (01) by means of eyelets (24) During the use the bush (22) is adjusted axially over length of the pipe to suit the depth of the hole in stud/bolt & locked there by means of cheese head screw (21) The stud/bolt heater is inserted in the hole of the stud/bolt & left there. Electrical supply connections are given from power supply of appropriate wattage at 24 volts to the terminals formed at bolt (16) and bolt (16a) and the power is switched on. The circuit is completed through connecting strip (03), lead (06), top plug (08), carbon /graphite resistance (09), plug (10), Pipe (11),"L Bracket (04) and terminal at bolt (16a). The carbon/graphite resistance (09) gets heated to about 7 1500 degree c & heats the pipe (11) by radiation. The pipe being in metal to metal contact with the stud/bolt heats up the stud/bolt faster due to high temperature achieved. Due to use of carbon/graphite resistor required watt density can be achieved at low voltage of 24 volts D.C which makes the stud/bolt heater entirely safe, compact and easy for use. 8 WE CLAIM: 1. An improved stud/bolt heater with carbon/graphite resistance (09) as heating element push fitted, at one end in axial blind hole in a plug (10) being welded to the upper pipe (11) encasing the total resistance assembly, the resistance (09) being electrically insulated from pipe (11) by insulating porcelain sleeve (07) other end of the resistance (09) being electrically connected to a top plug (08), which is electrically connected to a lead (06) connected to connecting strip (03), fastened to it by a threaded nut (05a) & check nut (05) the connecting strip supported on the main supporting "L" bracket (04) by insulated joint and further extending from an electrical supply connection, "L" bracket (04) being provided with bolt (16a), nut (17a) and washer (18a), the link strip (12), having connecting terminal formed by bolt (16), nut (17) and washer (18), the link strip (12) being provided for proper electrical contact the cover fixed with cheese head screw to the "L" bracket to support porcelain insulator (02) provided with a spring guide (26) and a spring (25) guided in it so as to retain the resistance assembly in pipe but to allow for the thermal expansion of the said resistance assembly and keeping it insulated it in case the assembly expands/ elongated thermally to reach the part of the cover (01) above it, by means of the porcelain insulator (02), the other electrical supply connections being formed on "L" bracket (04), the porcelain insulator (02) affixed to cover (01) by rivet (20) : the said pipe (11) provided with a axially slidable bush (22) on its outer diameter, the bush being with a locking screw (21). 2. The stud/bolt heater described in claim 1 having carbon/graphite resistance (09) as heating element where the heating element can withstand temperature of about 1500c, the top plug (08), plug (10) and lead (06) which being the parts coming in contact with the resistance (09) and getting heated to high temperature being made up of metals viz. tungsten, molybdenum or the like, the pipe being made of corrosion resistance metal like suitable stainless steel, the carbon/graphite resistance (09) radiating the heat to the 9 pipe (11) to heat the pipe (11) which in tern heats the stud/bolt being in metal to metal contact with it. 3. The stud/bolt heater as claimed in claim 1 and claim 2 having a connecting strip (03) connecting the lead (06) and the connecting terminal formed by bolt (16), nut (17) and washer (18) being provided with a link strip (12) made of electrically good conducting metal like copper, to provide proper electrical contact between electrical supply and the lead (06), the connecting strip (03) being made with multiple "U" bends to allow minimum amount of heat to reach the terminal and also to impart the connecting strip flexibility. 4. The stud/bolt heater as claimed in claim 1 having cover (01), the said cover bent "U" shape (14) to cover and protect the electrical contacts. 5. The stud/bolt heater as claimed in claim 1 provided with a bush (22) slidably fitted on outer diameters of the pipe, the bush having stepped diameter forming a collar, the smaller diameter of the two steps being used for locating the bush and consequently the stud/bolt heater in the hole of he stud/bolt, while a radial threaded hole being provided on the larger of the two stepped diameters so as to facilitate locking of the bush on the pipe by means of cheese head screw (21) provided, in suitable axial position. 6. The stud/bolt heater as claimed in claim 1 provided with electrical connection for connecting to electric supply of 24V and suitable wattage by providing bolt (16a), nut (17a) and washer (18a) on the "L" bracket and other terminal by providing bolt (16), nut (17), washer (18) and link strip (12) on the connecting strip (03). 7. The stud/bolt heater claimed in claim 1 where the said insulated joint between the "L" bracket (04) and connecting strip (03) is being achieved by using two insulated spacers (13), through which the bolt (15) is passed 10 through, extending through the hole in the connecting strip (03) being affixed at the end by a washer (18b) and nut (17b). ith Dated this 26m day of July, 2001 11 FOR BABUBHAI KANTILAL DOSHI. By their Agent (MANISH SAURASTRI) KRISHNA & SAURASTRI

Documents:

714-mum-2001-cancelled pages(25-08-2006).pdf

714-mum-2001-claims(granted)-(25-08-2006).doc

714-mum-2001-claims(granted)-(25-08-2006).pdf

714-mum-2001-correspondence(05-01-2007).pdf

714-mum-2001-correspondence(ipo)-(21-04-2008).pdf

714-mum-2001-drawing(31-10-2001).pdf

714-mum-2001-form 1(26-07-2001).pdf

714-mum-2001-form 18(11-08-2005).pdf

714-mum-2001-form 2(granted)-(25-08-2006).doc

714-mum-2001-form 2(granted)-(25-08-2006).pdf

714-mum-2001-form 3(26-07-2001).pdf

714-mum-2001-form 5(26-07-2001).pdf

714-mum-2001-power of attorney(26-07-2001).pdf

abstract1.jpg