Roller for a tracked vehicle, tracked vehicle provided with said roller and process for producing said roller

Abstract

The roller (10,10*,10") according to the invention is configured for rolling and resting against a continuous track of a tracked vehicle, and comprising a plurality of roller parts (100, 101, 102; 100*, 101*, 102*; 100", 102") wherein the roller (10,10*,10") is obtained with a process comprising the following steps: Sl.l) providing said plurality of roller parts (100, 101, 102; 100*, 101*, 102*; 100", 102"), at least one of which is obtained by forging; SI.2) welding said plurality of roller parts (100, 101, 102; 100*, 101*, 102*; 100", 102") one with another. It reduces manufacturing costs and renders the manufacturing process more flexible.

Description

[0001] ROLLER FOR A TRACKED VEHICLE , TRACKED VEHICLE PROVIDED

[0002] WITH SAID ROLLER AND PROCESS FOR PRODUCING SAID ROLLER

[0003] Field of the invention

[0004]

[0001] The present invention relates to a roller for a tracked vehicle , to a tracked vehicle provided with one or more of said rollers and to a process for manufacturing said roller .

[0005]

[0002] Said roller is particularly suited for producing the so-called miniloader and similar small construction vehicles .

[0006] Background art

[0007]

[0003] Small earth moving machines are becoming very popular for their versatility and low price .

[0008]

[0004] A first kind of such machines are the so-called Compact Track Loaders , generally characterised by a weight comprised between about 3000-6000 kg and an installed power comprised between about 55-105 horse power .

[0009]

[0005] A second kind of current small earth moving machines are the so-called mini-loader, generally characterised by a weight comprised between about 1000-3000 kg and an installed power comprised between about 20-50 horse power .

[0010]

[0006] Small earth moving machines , and in particular Compact Track Loaders and miniloader, can be wheeled- or tracked vehicles .

[0011]

[0007] Known tracked miniloaders are provided with an undercarriage and a continuous track .

[0012]

[0008] Such undercarriage in its turn comprises a driving wheel , one or more - for example two- idler wheels and a plurality of rollers .

[0009] The rollers roll over or under the continuous track and rest against it ; rollers furthermore engage with longitudinal protrusions formed by the continuous track so as to keep the latter relatively straight and aligned, reducing the lateral deformation of the continuous track ( lateral directions are perpendicular or transversal to the main direction of forward motion of the vehicle ) and preventing the track to detach from the rollers -so- called detracking ( " sci ngola tura" in Italian language ) .

[0013]

[0010] Roll ers of mini-loaders are currently made as one integral body of cast iron -an example of a known roller of a mini-loader is shown in Figure 1 as referred to with the overall reference 1 .

[0014]

[0011] Some drawbacks of this measure are the poor mechanical properties of cast iron and a limited production capability due to the casting production ef ficiency .

[0015]

[0012] In fact the manufacture of a cast roll is relatively laborious , more time-consuming and expensive than it might appear, even with automatic production equipment : one core needs to be made and then destroyed for each roll to be cast ; expensive multi-cavity casting apparatures are necessary for keeping the cycle time short in spite of the time needed for allowing the cast metal to solidi fy; the cast semimanufactured part generally has a very inaccurate shape and needs thorough machining for reaching the desired final shape and tolerances , with relative further time and costs .

[0016]

[0013] For example , very often rough semimanufactured rollers do not even have an axial through bore 3 but only a blind bore , and the axial through bore 3 needs to be obtained with expensive and time-consuming drilling steps ( Figure 1 ) .

[0017]

[0014] Furthermore known semi-manufactured cast rollers need to be heat treated before machining, usually austempered; austempering process requires a dedicated plant , which increases the production costs , binds the roller manufacturer to a few specific providers -often only one- and renders the supply chain more rigid .

[0018] Finally casting is a very energy-consuming process and in most cases has quite a high carbon foothprint .

[0019]

[0015] A scope of the present invention is overcoming the above described drawbacks of the state of the art and in particular providing a roller for a tracked vehicle which is obtained with a less expensive , less time-consuming and / or simpler process , without excessively worsening or even enhancing the mechanical properties of the roller .

[0020] Summary of the invention

[0021]

[0016] This scope is achieved, according to a first aspect of the present invention, with a roller having the features according to claim 1 .

[0022]

[0017] In a second aspect of the invention, this scope is achieved with a tracked vehicle having the features according to claim 13.

[0023]

[0018] In a third aspect of the invention, this scope is achieved with a Process for producing a roller for a tracked vehicle having the features according to claim 15 .

[0024]

[0019] The dependent claims are directed to further features of the invention .

[0025]

[0020] The advantages which can be achieved with the present invention will appear more evident for the skilled reader, from the following detailed description of a particular and non limiting embodiment , described with reference to the following schematic figures .

[0026] List of Figures

[0027] Figure 1 shows a partially sectioned view of a known roller for a miniloader, according to an ideal section plane crossing the rotation axis AXR of the roller ;

[0028] Figure 2 shows a perspective view of a miniloader according to a first particular embodiment of the present invention;

[0029] Figure 3 shows a partially sectioned view of an assembled roller of the tracked vehicle of Figure 2 , according to an ideal section plane crossing the rotation axis AXR of the roller ;

[0030] Figure 3A shows an enlarged detail of Figure 3 ;

[0031] Figure 4 shows a partially sectioned, exploded view of the roller of Figure 3 ;

[0032] Figure 5 shows a partially sectioned view of an assembled roller according to a second particular embodiment of the invention, configured for being assembled for example in the tracked vehicle of Figure 2 ;

[0033] Figure 6 shows a partially sectioned view of an assembled roller according to a third particular embodiment of the invention, configured for being assembled for example in the tracked vehicle of Figure 2 .

[0034] Detailed description

[0035]

[0021] Figures 2-4 relate to a roller for a tracked vehicle , and to a tracked vehicle provided with one or more of said roller, according to a first particular embodiment of the invention .

[0036]

[0022] Said roller is referred to with the overall reference 10 , 10 ’ , 10" and, according to an aspect of the present invention, is configured for rolling resting against a continuous track 1001 of a tracked vehicle 1000, and comprising a plurality of roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102".

[0037]

[0023] The tracked vehicle 1000 can comprise an undercarriage assembly (not shown) , a chassis 1015 forming a driver's compartment 1017 and a dozer blade 1019 (Figure 2) .

[0038]

[0024] The driver's compartment 1017 can house a steering wheel and / or other levers, press buttons and other command interfaces allowing a driver to manually steer and drive the vehicle 1000.

[0039]

[0025] Like in the embodiment of Figure 2 the driver's compartment 1017 can be open at its top and form a sort of pulpit.

[0040]

[0026] In other embodiments (not shown) the driver's compartment 1017 can form a substantially closed cab or cage, provided with one or more doors and / or one or moor windows .

[0041]

[0027] The blade 1019 can be driven by one or more mechanical arms 1111.

[0042]

[0028] In some embodiments or operating conditions the blade 1019 can be absent and be replaced for example by a bucket, a hook, a gripper, an auger or other mechanical tools .

[0043]

[0029] The undercarriage assembly can comprise a continuous crawler track 1001, a driving wheel 1137, one or more -for example two- idler wheels 1134, 1136 and a plurality of roller assemblies.

[0044]

[0030] Each roller assembly comprises a roller 10,10' , 10".

[0045]

[0031] The continuous crawler track 1001 can be made for example mostly of rubber or another elastomeric material -for example as an annular belt of rubber or elastomeric material- or mostly made of metal parts, for example comprising a plurality of links articulated together so as to form an annular chain, wherein said links are for example made of steel or other metals; said links can be connected together and articulated for example through suitable pins.

[0046]

[0032] The driving wheel 1137 is configured for engaging with the internal side of a respective continuous crawler track 1001 and driving said crawler track 1001, for example causing the latter to slide or more generally run relative to the chassis 1015.

[0047]

[0033] The driving wheel 1137, each idler wheel 1134, 1136 and each roller 10,10’ , 10" can be fixed to the undercarriage frame or directly to the chassis 1015.

[0048]

[0034] Each roller 10,10', 10" has an external diameter preferably smaller than the diameter of the driving wheel 1137 and the idler wheels 1134, 1136.

[0049]

[0035] The rollers 10,10', 10" are arranged for rolling against the stretch of continuous crawler track 1001 lying preferably between the driving wheel 1137 and one of the idler wheels 1136, 1137.

[0050]

[0036] The driving wheel 1137, each idle wheel 1134, 1136 and each roller 1001 are configured for rotating around respective rotation axes and for rolling over or under the internal side of a respective continuous crawler track 1001.

[0051]

[0037] These rotation axes are substantially horizontal and / or substantially parallel to the ground over which the vehicle 1000 travels or lies.

[0052]

[0038] The compact tracked loader 1000 preferably comprises at least one internal combustion engine (not shown) and / or one or more electric or hydraulic motors (not shown) for driving each driving wheel 1137 and more generally powering the continuous tracks 1001 , the undercarriage assembly, the blade 1019 or other mechanical tools or implements , mechanical arms 1111 and the tracked vehicle 1000 in general .

[0053]

[0039] The tracked vehicle is preferably a so-called miniloader .

[0054]

[0040] In the present description a vehicle having one or more of the following features is considered a miniloader :

[0055] -a weight comprised between about 1000-3000 kg; and / or -an installed power comprised between about 20-50 horse power .

[0056]

[0041] The rollers 10 , 10 ’ , 10" roll over or under the continuous track 1001 and rest against it .

[0057]

[0042] The rollers 10 furthermore engage with protrusions formed by the continuous track 1001 so as to keep the latter relatively straight and aligned, reducing the lateral deformation of the continuous track 1001 ( lateral directions are perpendicular or transversal to the main direction of forward motion of the vehicle , that is along the direction Y with reference to Figure 2 ) and preventing the track to detach from the rollers -so-called detracking- or at least reducing the risks of detracking .

[0058] Detracking prevents the vehicle from operating and needs a relatively long repair operation .

[0059]

[0043] Said protrusions formed by the continuous track

[0060] 1001 can for example enter and engage with the later described circumferential grooves 1012 , 1013 of the roller 10 .

[0061]

[0044] The roller 10 , 10 ’ , 10" is obtained with a process comprising the following steps:

[0062] 51.1) providing said plurality of roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" at least one of which is obtained by forging ;

[0063] 51.2) welding said plurality of roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" one with another.

[0064] Forging is preferably hot forging or warm forging but it can be for example cold forging too.

[0065]

[0045] Preferably the roller 10,10’ , 10" comprises three roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" but in other particular embodiments (not shown) can comprise also a different number of roller parts, for example two, four, five, six, seven, eight, nine, ten or more roller parts.

[0066]

[0046] Preferably all of the roller parts, among which for example roller parts 100, 101, 102, are obtained by forging .

[0067]

[0047] The roller 10,10’ , 10" is configured for rotating around a predetermined rotation axis AXR when assembled on the tracked vehicle 1000.

[0068]

[0048] Each roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" preferably forms a segment of the roller which forms an axial section of said roller, that is extends along and over a portion of the rotation axis AXR.

[0069]

[0049] Preferably in the assembled roller 10,10’ , 10" the roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" are all co-axial with the rotation axis AXR (Figure 3) .

[0070]

[0050] Preferably some of said roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" or each roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" is delimited, externally and / or internally, substantially by a surface of revolution obtained rotating a generatrix around axis AXR (Figure 3, 4) .

[0071]

[0051] In combination on alternatively some of said roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" or each roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" is preferably delimited by a surface having a radial symmetry around the rotation axis AXR.

[0072]

[0052] Preferably some of said roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" or each roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" is obtained through forging, for example through hot forging, warm forging or cold forging.

[0073]

[0053] Preferably the roller 10,10’ , 10" is obtained by welding said at least two, at least three or all of said roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" one with another.

[0074]

[0054] Preferably at least one of said roller parts -and more preferably all of them- forms / form one or more of the following elements:

[0075] -an axial bore 1003, 1004, 1005 extending through the respective roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" and which extends along the rotation axis AXR; and

[0076] -a flange 1006, 1007, 1008 which, at least in some crosssections of the roller part 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102", extends around the rotation axis AXR in such a way to surround the rotation axis AXR.

[0077]

[0055] At least when the roller parts 100, 101, 102; 100’ , 101’ , 102’ ; 100", 102" are ready to be assembled one with another, the axial bores 1003, 1004, 1005 are preferably through-bores.

[0078]

[0056] Preferably in the assembled roller 10,10’ , 10" the axial bores 1003, 1004, 1005 are co-axial one to another so as to form a through bore 30 configured for being crossed and contain a pin (not shown) around which the roller 10,10', 10" can rotate (Figure 3) .

[0079]

[0057] Preferably each flange 1006, 1007, 1008 completely surrounds the rotation axis AXR.

[0080]

[0058] Each flange 1006, 1007, 1008 can have substantially the shape of a circumferential, radial rib -like the flange 1007 of Figure 4- or a substantially conical, tapered even tubular or trumpet-like protrusion, like protrusions 1006, 1008 of Figure 4.

[0081]

[0059] In the assembled roller 10 the flanges 1006, 1007, 1008 are axially spaced apart one from another by respective circumferential grooves 1012, 1013 (Figure 3) .

[0082]

[0060] Preferably the roller 10,10' , 10" comprises two end parts 100, 102 and a middle part 101 (Figure 4) .

[0083]

[0061] The two end parts 100, 102 have advantageously and substantially the same overall shape (Figure 4) .

[0084]

[0062] Preferably the middle part 1007 has a substantially bilateral symmetry with respect to a symmetry plane SP substantially perpendicular to the rotation axis AXR and crossing axis AXR in the middle point of the axis portion over which the middle part 1007 extends (Figure 4) .

[0085]

[0063] Advantageously one or more of the roller parts, and preferably at least the end parts 100, 102 and the middle part 101, form at least one tubular end 1009, 1010, 1011

[0086] ( Figure 4 ) .

[0087]

[0064] Each tubular end 1009, 1010, 1011 can substantially have the shape of a bushing (Figure 4) .

[0088]

[0065] Each tubular end 1009, 1010, 1011 preferably forms at least a portion of the respective axial bores 1003, 1004, 1005 (Figure 4) .

[0066] Each tubular end 1009 of the end portions 100, 102 is advantageously configured for being fitted in a respective end of the axial bore 1004 of the middle part 101.

[0089]

[0067] Each tubular end 1009 of the end portions 100, 102 is advantageously configured for being fitted in the axial bore 1004 of the middle part 101 by a depth LX1, LX2 preferably equal to or greater than 0,04 times the diameter DSM of the axial bore 1004 (Figure 3) .

[0090]

[0068] Said ratios LX1 / DSM and LX2 / DSM are more preferably equal to or greater than 0,07 and even more preferably equal to or greater than 0,15; 0,25; 0,30; 0,31 or 0,33.

[0091]

[0069] Said ratios LX1 / DSM and LX2 / DSM are more preferably smaller than 1, and even more preferably smaller than 0,7 or 0,6 or 0,5 or 0,33 or 0,15 or 0,14.

[0092]

[0070] Over the axial length in which the tubular ends 1009 are fitted in the through bore 1004, the radial thickness RT1 of the tubular ends is equal to or greater than 0,07 times the diameter DSM.

[0093]

[0071] The ratio RT1 / DSM is more preferably equal to or greater than between 0,09 times, and even more preferably equal to or greater than the diameter DSM, 0,10 times the diameter DSM, 0,13 times the diameter DSM or 0,14 times the diameter DSM.

[0094]

[0072] The ratio RT1 / DSM can be for example equal to or smaller than 0,5 times, ot 0,4 times, 0,3 times or 0,2 times .

[0095]

[0073] The ratio RT1 / DSM can be for example comprised between 0,11-0,22 or between 0,13-0,22; 0,21-0,22 times.

[0096]

[0074] Over the axial length in which the tubular ends 1009 are fitted in the through bore 1004, the radial thickness RT2 of the tubular ends is equal to or greater than 0,04 times the diameter DSM.

[0097]

[0075] The ratio RT2 / DSM is more preferably equal to or greater than between 0,07 times, and even more preferably equal to or greater than 0,09 times the diameter DSM, equal to or greater than the diameter DSM, equal to or greater than 0,10 times, 0, 11 times , 0, 14 times or 0, 16 times the diameter DSM.

[0098]

[0076] The ratio RT2 / DSM can be for example equal to or smaller than 0,5 times, 0,4 times, 0,3 times, 0,2 times, 0,17 times or 0,1 times.

[0099]

[0077] The end parts 100, 102 and the middle part 101 are assembled toghether preferably welding the edges of the tubular ends 1010, 1011 with the shoulder 10091 delimiting the tubular end 1009, when the tubular ends 1009 are fitted in the tubular ends 1010, 1011 (Figure 3A) .

[0100]

[0078] This is done forming a welding seam 1018 which extends around the whole circumference of some crosssections of the assembled roller 10,10’ , 10".

[0101]

[0079] The welding seam 1018 can form for example one continuous line of fused metal or a succession of spots or lines of molten metal.

[0102]

[0080] Preferably the tubular ends 1009 are fit in the through bore 1004 with a light interference for holding in position more firmly the parts during handling and welding .

[0103]

[0081] Such light interference is obtained preferably through press fitting.

[0104]

[0082] Such light interference is comprised between 0,00- 0,090 and more preferably between 0,00-0,065 millimetres over the diameter.

[0105]

[0083] The above features of interference fitting do not deform the inner through bore 30 of the roller 10, 10', 10" and preserve concentricity of the axial through bores of roller segments 100, 101, 102; 100' , 101' , 102' ; 100", 102".

[0106]

[0084] The previous measures greatly increase the flexural strength of the roller 10,10' , 10" at the same time keeping the costs of assembling process low.

[0107]

[0085] In particular welding forged parts is much less energy consuming than casting the final part.

[0108]

[0086] Preferably the assembled roller 10,10' , 10" has one or more of the following features:

[0109] -an overall length LR comprised between 80-170 millimetres and more preferably comprised between 100- 160 millimetres, between 105-150 millimetres, between 105-140 millimetres or between 105.135 millimetres;

[0110] -a maximum diameter DR comprised between 110-180 millimetres and more preferably comprised between 120- 170 millimetres, between 125-165 millimetres;

[0111] -an overall weight comprised between 8,0-35,0 kilograms and more preferably between 10,0-32,0 kilograms or between 12,6-28,0 kilograms.

[0112]

[0087] Preferably the assembled roller 10,10' , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of quenched and tempered steel or of a microalloyed steel, such as for example a microalloyed steel having one or more of the following features:

[0113] -a content of carbon comprised between 0,1-0, 7 %wt;

[0114] -a content of manganese comprised between 0,6-2 % wt;

[0115] -a content of silicon equal to or lower than 1,3 % wt -a content of chromium equal to or lower than 0,8 % wt -a content of sulfur equal to or lower than 0,1 % wt -a content of phosphorus equal to or lower than 0,05 % wt ;

[0116] -a content of molybdenum equal to or lower than 0,13 % wt

[0117] -a content of nitrogen equal to or lower than 0,04 % wt -a content of niobium equal to or lower than 0,07 % wt -a content of vanadium equal to or lower than 0,4 % wt; -wherein said contents are the weight percent of the corresponding substance.

[0118]

[0088] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0119] -a content of carbon comprised between 0,15-0,5 %wt;

[0120] -a content of manganese comprised between 1-2 % wt;

[0121] -a content of silicon comprised between 0,05-1 % wt

[0122] -a content of chromium equal to or lower than 0,6 % wt -a content of sulfur comprised between 0,01-0,08 % wt -a content of phosphorus equal to or lower than 0,04 % wt

[0123] -a content of molybdenum equal to or lower than 0,1 % wt -a content of nitrogen equal to or lower than 0,03 % wt -a content of vanadium equal to or lower than 0,3 % wt; -a content of titanium equal to or lower than 0,001% wt or 0, 006 % wt .

[0124]

[0089] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0125] -a content of carbon comprised between 0,4-0, 5 %wt; -a content of manganese comprised between 1-1,8 % wt;

[0126] -a content of silicon comprised between 0,1-0, 9 % wt -a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,015-0,07 % wt -a content of phosphorus equal to or lower than 0,035 % wt

[0127] -a content of molybdenum equal to or lower than 0,09 % wt

[0128] -a content of nitrogen comprised between 0,005-0,03 % wt -a content of vanadium comprised between 0,05-0,3 % wt .

[0129]

[0090] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0130] -a content of carbon comprised between 0,42-0,49 %wt;

[0131] -a content of manganese comprised between 1,2-1, 6 % wt;

[0132] -a content of silicon comprised between 0,15-0,8 % wt -a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,02-0,06 % wt -a content of phosphorus equal to or lower than 0,025 % wt

[0133] -a content of molybdenum equal to or lower than 0,08 % wt

[0134] -a content of nitrogen comprised between 0,01-0,02 % wt -a content of vanadium comprised between 0,08-0,2 % wt .

[0135]

[0091] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0136] -a content of carbon comprised between 0,43-0,47 %wt; -a content of manganese comprised between 1,3-1, 5 % wt; -a content of silicon comprised between 0,3-0, 6 % wt -a content of chromium equal to or lower than 0,2 % wt; -a content of sulfur comprised between 0,03-0,05 % wt -a content of phosphorus equal to or lower than 0,015 % wt ;

[0137] -a content of molybdenum equal to or lower than 0,06 % wt

[0138] -a content of nitrogen comprised between 0,01-0,016 % wt -a content of vanadium comprised between 0,1-0,17 % wt .

[0139]

[0092] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0140] -a content of carbon comprised between 0,15-0,5 %wt; -a content of manganese comprised between 1-2 % wt; -a content of silicon comprised between 0,05-1 % wt -a content of chromium equal to or lower than 0,6 % wt -a content of sulfur comprised between 0,01-0,08 % wt -a content of phosphorus equal to or lower than 0,04 % wt

[0141] -a content of molybdenum equal to or lower than 0,1 % wt -a content of nitrogen equal to or lower than 0,03 % wt -a content of vanadium equal to or lower than 0,3 % wt; -a content of titanium equal to or lower than 0,001% wt or 0, 006 % wt .

[0142]

[0093] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features : -a content of carbon comprised between 0,4-0, 5 %wt; -a content of manganese comprised between 1-1,8 % wt; -a content of silicon comprised between 0,1-0, 9 % wt -a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,015-0,07 % wt -a content of phosphorus equal to or lower than 0,035 % wt

[0143] -a content of molybdenum equal to or lower than 0,09 % wt

[0144] -a content of nitrogen comprised between 0,005-0,03 % wt -a content of vanadium comprised between 0,05-0,3 % wt .

[0145]

[0094] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features :

[0146] -a content of carbon comprised between 0,42-0,49 %wt; -a content of manganese comprised between 1,2-1, 6 % wt; -a content of silicon comprised between 0,15-0,8 % wt -a content of chromium equal to or lower than 0,3 % wt -a content of sulfur comprised between 0,02-0,06 % wt -a content of phosphorus equal to or lower than 0,025 % wt

[0147] -a content of molybdenum equal to or lower than 0,08 % wt

[0148] -a content of nitrogen comprised between 0,01-0,02 % wt -a content of vanadium comprised between 0,08-0,2 % wt .

[0149]

[0095] More preferably the assembled roller 10,10’ , 10" and / or one or more of its end parts 100, 102, its middle part 101 and / or other roller parts are made of a microalloyed steel having one or more of the following features : -a content of carbon comprised between 0,43-0,47 %wt;

[0150] -a content of manganese comprised between 1,3-1, 5 % wt;

[0151] -a content of silicon comprised between 0,3-0, 6 % wt

[0152] -a content of chromium equal to or lower than 0,2 % wt; -a content of sulfur comprised between 0,03-0,05 % wt -a content of phosphorus equal to or lower than 0,015 % wt ;

[0153] -a content of molybdenum equal to or lower than 0,06 % wt

[0154] -a content of nitrogen comprised between 0,01-0,016 % wt -a content of vanadium comprised between 0,1-0,17 % wt .

[0155]

[0096] A shaft, bearings and seals can be assembled to the roller 10,10’ , 10" and then possibly offered for sale or provided to a manufacturer of miniloaders or other tracked vehicles.

[0156]

[0097] In that case the roller 10, 10' , 10"is assembled preferably coaxial- with said shaft in such a way to be able to rotate around said shaft and bearings, if any.

[0157]

[0098] An assembly comprising the roller 10,10' , 10" said shaft and possibly said bearings and / or said seals is conventionally referred to as "completed roller" in the present description.

[0158]

[0099] According to a preferred embodiment, the roller 10,10' , 10" is obtained through a process in which the end parts 100, 102, the middle part 101 and / or other roller parts of the roller 10,10' , 10" undergo the following steps, in order:

[0159] 510.1) said parts are obtained by forging, possibly microforging; said parts are then preferably quenched and tempered;

[0160] 510.2) said parts are machined;

[0161] 510.3) said parts or possibly only portions thereof are induction hardened;

[0162] S10.4) said parts are welded one to another.

[0163] Step S10.2) can be advantageously made in such a way to render further machining operations after welding unnecessary, lowering the costs of the production process .

[0164]

[0100] Advantageously step S10.3) is avoided, rendering the manufacturing process cheaper and leaner.

[0165]

[0101] Possibly he roller obrained from step S10.4) can be further machined.

[0166]

[0102] According to a preferred embodiment, the end parts 100, 102, the middle part 101 and / or other roller parts of the roller 10,10’ , 10" are made of a microalloyed steel, preferably having one or the previously described compositions, and the roller 10,10’ , 10" is obtained through a process in which the end parts 100, 102, the middle part 101 and / or other roller parts of the roller 10,10’ , 10" undergo the following steps, in order:

[0167] Sil .1) said parts are obtained by forging and subsequent controlled cooling;

[0168] 511.2) said parts are machined;

[0169] 511.3) said parts are welded one to another.

[0170] Such controlled cooling can take place in ambient atmosphere, controlling the cooling air flow for example with simple fans or capturing hoods.

[0171]

[0103] This latter process is very lean, cheap and avoids the steps of induction hardening and machining the welded product .

[0172]

[0104] The previous teachings allow to obtain a roller 10,10’ , 10" having mechanical strenght, surface hardness and wear resistance comparable with or better than current casted rollers 1 through a less expensive and energy consuming manufacturing process.

[0173]

[0105] Such manufacturing process can be organizes much more flexibly, exploiting much more widespread technologies which do not rigidly tie a roller manufacturer to a specific supplier or supply chain.

[0174]

[0106] A surface of the roller 10, 10' , 10"can reach a hardness of about 300 Brinell and in some portions even 50 HRC (Rockwell C) .

[0175]

[0107] The previously described processes for manufacturing the roller 10,10' , 10" need much less energy for melting the metals; hence are cheaper and have a lower carbon foothprint than obtaining known rollers 1 through casting.

[0176]

[0108] The embodiments previously described can be modified in several ways without departing from the scope of the present invention.

[0177]

[0109] For example in a particular embodiment, not shown, the tubular ends 1010, 1011 can be fit in the tubular end 1009 when the tubular ends 1009.

[0178]

[0110] In a particular embodiment of the invention the roller 10' can comprise a plurality of roller parts 100' , 101' , 102', and the middle segment 101' or other part 101' can form no flange 1007 (Figure 5) .

[0179]

[0111] In a particular embodiment of the invention the roller 10 can comprise only a first 100" and a second segment 102" while the middle segment 101, 101' can be absent (Figure 6) ; in that case the first 100" and the second segment 102" can be integrally fixed one to another, for example by welding.

[0180]

[0112] The f irst 100" and the second segment 102" can be fit one into another (Figure 6) .

[0181]

[0113] Each of the first 100" and second segment 102" can form a respective flange 1006, 1008.

[0182]

[0114] All constructional details can be replaced with technically equivalent elements.

[0183]

[0115] A wording such as "A comprises B, C, D" or "A is made up of B, C, D" is to be understood as encompassing and disclosing the particular case of "A consists of B, C, D".

[0184]

[0116] Wordings such as "A comprises an element B" when not differently specified is to be understood as "A comprises one or more elements B" .

[0185]

[0117] Mentions of a "first, second, third... n-th entity" merely intend to distinguishing the entities one from another but the mention of a n-th entity does not necessarily imply the existence of a first, second, third ... (n-l)-th entity.

[0186]

[0118] Examples and lists of possible alternatives are to be understood as non-exhaustive .

Claims

- 22 -CLAIMS1) Roller (10, 10’ , 10") configured for rolling and resting against a continuous track of a tracked vehicle, and comprising a plurality of roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") wherein the roller ( 10 , 10 ’ , 10" ) is obtained with a process comprising the following steps:51.1) providing said plurality of roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") , at least one of which is obtained by forging;51.2) welding said plurality of roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") one with another.2) Roller according to claim 1, comprising at least two or at least three roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") , wherein at least one of the at least two or at least three roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") provided in step Sl.l) is obtained by forging.3) Roller according to claim 2, wherein all of the at least two or at least three roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") provided in step Sl.l) are obtained by forging.4) Roller according to one or more preceding claims, wherein at least two of said roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") are roller segments, each of which forms an axial section of said roller.5) Roll er according to claim 4, wherein at least two oral least three of said roller parts (100, 101, 102; 100’ ,101’ , 102’ ; 100", 102") are roller segments, each of which forms an axial section of said roller.6) Roller according to claim 4 or 5, wherein said roller segments are coaxial one relative to another and to a predetermined rotation axis (AXR) .7) Roller according to claim 4 or 5 or 6, wherein at least one of said roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") forms one or more of the following elements:-an axial bore (1003, 1004, 1005) extending through the roller part and extending along a predetermined rotation axis (AXR) ; and-a flange (1006, 1007, 1008) which, at least in some cross-sections of the roller part (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") , extends around the rotation axis (AXR) surrounding said axis (AXR) .8) Roller according to one or more preceding claims, wherein at least one of said roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") is made of a quenched and tempered steel or of a microalloyed steel.9) Roller according to one or more preceding claims, wherein at least one of said roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") is made of a steel having one or more of the following features:-a content of carbon comprised between 0,1-0, 7 %wt;-a content of manganese comprised between 0,6-2 % wt; -a content of silicon equal to or lower than 1,3 % wt -a content of chromium equal to or lower than 0,8 % wt-a content of sulfur equal to or lower than 0,1 % wt-a content of phosphorus equal to or lower than 0,05 % wt ;-a content of molybdenum equal to or lower than 0,13 % wt-a content of nitrogen equal to or lower than 0,04 % wt -a content of niobium equal to or lower than 0,07 % wt -a content of vanadium equal to or lower than 0,4 % wt; -wherein said contents are the weight percent of the corresponding substance.10) Roller according to one or more preceding claims, having one or more of the following features:-an overall length (LR) comprised between 80-170 millimetres ;-a maximum diameter (DR) comprised between 110-180 millimetres ;-an overall weight comprised between 8,0-35,0 kilograms .11) Roll er according at least to claim 7, wherein:-at least a first part of said roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") fo rms at least one tubular end (1009, 1010, 1011) ;-at least a second part of said roller parts (100, 101) 102) forms said axial bore (1003, 1004, 1005) ;-said at least one tubular end (1009, 1010, 1011) is fitted in said axial bore (1003, 1004, 1005) and then welded to said second part (100, 101, 102) .12) Roller according at least to claim 11, wherein said at least one tubular end (1009, 1010, 1011) is welded to- 25 - said second part (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") with a welding seam (1018) which extends around the whole circumference of some cross-sections of the assembled roller (10,10’ , 10") .13) Tracked vehicle (1000) comprising at least one continuous crawler track (1001) and at least one roller having the features according to one or more claims 1- 11 and configured for rolling and resting against said continuous crawler track (1001) while said tracked vehicle (1000) travels.14) Tracked vehicle (1000) according to claim 13, having one or more of the following features:-a weight comprised between about 1000-3000 kg; and / or -an installed power comprised between about 20-50 horse power .15) Process for producing a roller (10,10’ , 10") for a tracked vehicle, comprising the following steps:51.1) providing a plurality of roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") , at least one of which is obtained by forging;51.2) welding said plurality of roller parts (100, 101, 102; 100’ , 101’ , 102’ ; 100", 102") one with another.

Images