Description:‘METHODOLOGY AND ARRANGEMENT FOR UNIFORM EXPANSION AND SAFE EXTRACTION OF LARGE SIZE INTERFERENCE FIT BEARINGS’

FIELD OF THE INVENTION:
[001] The present invention relates to Draw Bench operated Cold drawing mill of Seamless Steel tube manufacturing plant. More particularly, the present invention relates to methodology and arrangement for uniform and controlled heating for expansion and safe dismantling of large size interference fit bearings used in heavy duty gearboxes of Draw Bench machines in Cold Mill of seamless steel tube manufacturing plant.

BACKGROUND OF INVENTION/PRIOR ART:
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[003] Manufacturing of seamless steel tubes involves metal deformation processes during which the raw material [bloom/billet] is converted into a finished tube. The type and number of deformation processes can vary from process to process based on final specification [Outside diameter, wall thickness and length] of the tube. The process used involves four major metal deformation processes namely cross piercing and elongation, pushing, rolling in Hot Mill operations and the tubes which cannot be finished at Hot Mill involves cold drawing to finished size in Cold Mill.

[004] Cold drawing of hollow tubes at ambient temperature is carried out in Draw Bench machines. Cold drawing requires more axial load to finish the hollow tube to required size. The draw benches are fitted with heavy duty reduction gearboxes of larger size which can exert maximum output torque of about 3,90,000 Nm. The internals of the gearboxes are fitted with spherical roller bearings of internal diameter as large as 320 mm, outside diameter 540 mm and width 176 mm. Spherical roller bearings are fitted on shafts with interference fit of up to +0.15 mm. During servicing of gearboxes for rectification of defects in internals , bearings which are to be reused have to be dismantled without any damage and assembled back .Female part of interference fit machine components are uniformly heated up to 120°C for thermal expansion using oil bath and are fitted on the shafts .During dismantling , uniform heating of machine components up to 120°C within a short span of time is required so that significant temperature difference is maintained between male and female part . The female part expands by thermal expansion and eases dismantling without damage to mating surfaces. Also heating of bearings beyond 120°C is not recommended by the manufacturer. Direct flame heating of bearings for dismantling purpose is also not recommended as use of direct flame or blow torch to heat up bearing is risky, hazardous and causes uneven thermal expansion and/or material property distortion.

[005] Hence, there is a need to find out alternative way of controlled & uniform heating of bearing inner races within short span of time and arrangements for safe dismantling of bearings. Therefore, the present invention has been proposed.

OBJECTS OF INVENTION:
[006] An object of the invention is to provide methodology and arrangement for uniform and controlled heating of large size interference fit bearings with in short span of time for thermal expansion.

[007] Another object of the invention is to provide puller arrangement for safe extraction of large size interference fit bearings, which obviates shortcomings of the prior art(s).

[008] Still another object of present invention is to develop methodology and arrangement for uniform and controlled heating within short span of time and safe dismantling of large size interference fit bearings used in heavy duty machines.

[009] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF INVENTION:
[0010] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0011] The present invention comprises of resistance heating pads connected to electric heating controller unit with temperature feedback system for uniform and controlled heating of outer surface of inner race of bearings within a short span of time. A thin layer of about 1 mm thickness aluminum or other soft metal sheet is wrapped around the inner race. The resistance heating pads are wrapped around the inner race over the aluminum sheet. Aluminum or other soft metal sheet prevents direct contact of resistance heating pads to prevent any localized heating spots which will deteriorate the properties of bearing metal. The heating pads are energized by the electric heating controller unit and rate of heating and/or soaking in closed loop control system with thermocouple feedback can be set to achieve heating in a short span of time. Thermocouple feedback from shaft metal adjacent to bearing enables monitoring of shaft temperature and to decide on the soaking time required for the particular size of bearing. Customized puller arrangement with fabricated fixture and a hydraulic jack of Min 5 tons’ load capacity is used for ease and safe extraction of bearing inner race. Fixture arrangement comprises of circular half plates (Circular half plates connected by welding /bolting joint) with internal diameter matching to inner race on bearing end, full circular plate on hydraulic jack end, studs of sufficient diameter to connect the circular plates on both the ends. After controlled heating/soaking of bearing metal to 120°C and a significant temperature difference of 40 to 50°C is maintained between shaft and bearing metal, hydraulic pressure has to be applied to the jack. This method ensures uniform and controlled heating within short span of time thus enabling thermal expansion & safe dismantling of large size interference fit bearings used in heavy duty machines.

[0012] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

[0013] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0014] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
[0015] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:

Figure 1 shows: Bearing (2) fitted with interference fit on shaft (1).

Figure 2 shows: A thin aluminum sheet (4) wrapped around the bearing inner race (3) (Outer race, rollers, cage removed).

Figure 3 shows: Customized fixture arrangement with circular half plates (5) connected with welded or bolted joints, Circular plate (6), studs (7)- 4 nos to connect part no. (5) and (6).

Figure 4 shows: Shaft (1) with customized fixture, hydraulic jack (8) with hand pump (9) fixed between fixture and shaft (1) to act as customized bearing puller, flexible resistance heating pads (10) wrapped around aluminum sheet (4), electric heating controller unit (11) with current output cables (12) and thermocouple cables (13- feedback thermocouple from bearing metal, 14 – feedback thermocouple from shaft metal adjacent to bearing for purpose of temperature monitoring).

[0016] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0017] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0018] In the process of seamless steel tube manufacturing using Hot & Cold Mill process, cold drawing of hollow tubes from Hot Mill is carried out in draw benches. Cold drawing requires more axial load to finish the hollow tube to required size. The draw benches are fitted with heavy duty reduction gearboxes of larger size which can exert maximum output torque of about 3,90,000 Nm. The internals of the gearboxes are fitted with spherical roller bearings of internal diameter as large as 320 mm, outside diameter 540 mm and width 176 mm. Spherical roller bearings are fitted on shafts with interference fit of up to +0.15 mm. During servicing of gearboxes for rectification of defects in internals, bearings which are to be reused have to be dismantled without any damage and assembled back. Female part of interference fit machine components are uniformly heated up to 120°C for thermal expansion using oil bath and are fitted on the shafts. During dismantling, uniform heating of machine components up to 120°C within a short span of time is required so that significant temperature difference is maintained between male and female part. The female part expands by thermal expansion and eases dismantling without damage to mating surfaces. Also heating of bearings beyond 120°C is not recommended by the manufacturer. Direct flame heating of bearings for dismantling purpose is not recommended as use of direct flame or blow torch to heat up bearing is risky, hazardous and causes uneven thermal expansion and/or material distortion. Hence, there is a need to find out alternative way of controlled heating of bearing inner races and arrangements for safe dismantling of bearings.

[0019] Reference may be made to Figure 4, wherein customized puller arrangement comprising of fixture assembly and hydraulic jack with hand pump (8 and 9) located between shaft (1) and bearing inner race (3). Flexible resistance heating pads (10) is wrapped around aluminum sheet (4) which is wrapped on bearing inner race (3). Electric heating controller unit (11) is connected with current output cables (12) to flexible heating pads (10), thermocouple feedback cables (13) and (14) from bearing metal and shaft metal surface adjacent to bearing metal respectively.

[0020] Electric heating controller unit (11) can be programmed to attain controlled rate of heating of bearings up to 120°C with thermocouple feedback (13) and soaking time can be programmed and controlled by monitoring the raise in shaft temperature via thermocouple feedback (14). Controlled heating with closed loop feedback from thermocouples ensures bearing is not heated beyond 120°C. Wrapped aluminum sheet (4) protects the bearing surface from any possibility of localized heating and evenly wrapped flexible heating pads(10) around bearing surface ensures uniform heating of bearing metal .Resistance heating pads ensures rapid heating with short span of time .Once the bearing temperature reaches 120°C and the temperature difference between shaft (1) and bearing metal (3) is around 50 to 60°C, significant expansion of bearing inner diameter is attained due to thermal expansion and is free from interference fit. Hydraulic jack (8) is pressurized to extract the bearing inner race (3).

[0021] Customized bearing puller arrangement (5, 6, 7, 8 and 9) can be altered to fit on any size of bearing and ensures safe extraction of bearing (3) by applying hydraulic force between shaft (1) and bearing inner race (3). Hydraulic pressure can be applied once the temperature difference between bearing metal (3) and shaft (1) is in range of 50 to 60°C to enable extraction with least force.

[0022] Electric resistance heating unit (11) enables uniform and rapid heating of bearing metal (3) via flexible resistance heating pads (10) wrapped around the bearing periphery and controlled rate of heating of bearing metal (3) via thermocouple feedback (13). This prevents bearing metal deformation due to uneven expansion.

[0023] Localised heating of bearing rolling surface is prevented by using a thin layer of aluminium sheet (4) wrapped in between bearing metal (3) and resistance heating pad (10). This ensures that, bearing rolling surface hardness is retained even after heating and prevents deterioration of bearing material property.

[0024] Shaft temperature feedback obtained via thermocouple (14) enables to decide the soaking time required for the bearing metal (3).

[0025] The present invention enables uniform and rapid heating of bearing metal (3) ensuring sufficient expansion. Interference fit bearings of large size even with bearing bore diameter of above 400 mm can be extracted from interference fit shaft without crack/scoring mark on the bearing metal. This method enables safe dismantling and reuse of partial life interference fit bearings and other components used in heavy duty machine applications.

[0026] Controlled heating with closed loop feedback from thermocouples ensures bearing is not heated beyond 120°C. Wrapped aluminum sheet (4) protects the bearing surface from any possibility of localized heating and evenly wrapped flexible heating pads (10) around bearing surface ensures uniform heating of bearing metal. Resistance heating pads ensure rapid heating with short span of time. Once the bearing temperature reaches 120°C and the temperature difference between shaft (1) and bearing metal (3) is around 50 to 60°C, significant expansion of bearing inner diameter is attained due to thermal expansion and is free from interference fit. Hydraulic jack (8) is pressurized to extract the bearing inner race (3).

[0027] Customized bearing puller arrangement (5,6,7,8 and 9) and electric heating unit with resistance heating pads (10,11,12,13 and 14) enable uniform & controlled heating of bearing metal to 120°C and enables sufficient expansion of bearing metal (3) to ensure safe dismantling of larger size bearings assembled in interference fit without any minor damages like scoring marks on mating surfaces. This enables reuse of partial life bearings and other interference fit machine components.

TEST RESULT:

[0028] The following are the heating & soaking time using a 75kVA resistance heating unit for various bearing diameters for ease of dismantling the interference fit inner race. The maximum temperature to which inner race of bearing heated is 120°C and the temperature difference between inner race of bearing and the shaft is minimum 50 to 60°C to have comparatively more thermal expansion of inner race compared with the shaft and to have easier extraction of bearing inner race from shaft.

Bearing bore diameter (mm) Width (mm) Heating time(Min) Soaking Time (Min)
150 108 20 8
170 120 22 10
260 144 25 12
320 176 30 15

[0029] For other sizes of bearings, heating and soaking time can be determined by monitoring the raise in temperature of shaft and bearing inner race via feedback thermocouples.

WORKING OF THE INVENTION:

[0030] Electric resistance heating pads (10) are evenly wound around the bearing inner race (3) with a thin layer of 1 mm aluminum sheet (4). Electric resistance pads are connected to resistance heating controller unit (11) via power output cables (12). Raise in temperature of bearing inner race (3) and shaft (1) are monitored and controlled via feedback thermocouples (13) and (14) respectively. Bearing inner race is being heated upto 120°C and heating/soaking time is programmed and controlled by monitoring the temperature difference between the bearing inner race and shaft is within 50 to 60°C. This temperature difference between male and female shrink fit component is essential to achieve relatively more thermal expansion of female component compared with male component. Customized bearing puller arrangement (5, 6, 7, 8 and 9) can be altered to fit on any size of bearing and ensures safe extraction of bearing (3) by applying hydraulic force between shaft (1) and bearing inner race (3). Hydraulic pressure can be applied once the temperature difference between bearing inner race (3) and shaft (1) is in range of 50 to 60°C to enable extraction with least force. Electric resistance heating for uniform thermal expansion of shrink fit component followed by extraction with customized hydraulic puller arrangement enables easier and safer extraction of large sized interference fit bearings without any damage and ensures reuse of bearing after dismantling.

[0031] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0032] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.
[0033] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0034] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0036] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0037] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:WE CLAIM

1. Methodology and arrangement for uniform expansion and safe extraction of large size interference fit bearings comprises of:
fixture assembly and hydraulic jack (8) with hand pump (9) located between shaft (1) and bearing inner race (3), wherein flexible resistance heating pads (10) are wrapped around sheet (4) which is wrapped on bearing inner race (3), in which Electric heating controller unit (11) is connected with current input cables (12) to flexible heating pads (10), thermocouple feedback cables (13) and (14) are provided from bearing metal and shaft metal surface adjacent to bearing metal respectively.

2. The Methodology and arrangement as claimed in claim 1, wherein the Electric heating controller unit (11) is provided to attain controlled rate of heating of bearings up to 120°C with thermocouple feedback (13), and soaking time is set and controlled by monitoring the raise in shaft temperature via thermocouple feedback (14), in which a bearing (2) is fitted with interference fit on the shaft (1).

3. The Methodology and arrangement as claimed in claim 1, wherein the bearing puller arrangement (5,6,7,8, 9) is altered to fit on any size of bearing and ensures safe extraction of bearing (3) by applying hydraulic force between shaft (1) and bearing inner race (3), in which Hydraulic pressure is applied once the temperature difference between bearing metal (3) and shaft (1) is in range of 50 to 60°C to enable extraction with least force.