Flóra Hajdu Bearings - PowerPoint Presentation

Flóra Hajdu Bearings B406 hajdfl@sze.hu

Content Bearings typesBeairing mountsPreassembled bearing units2019. 03. 20. Hajdu Flóra

Bearings Bearings permit smooth, low-friction movement betweentwo surfaces The movement can be either rotary (a shaftrotating within a mount) or linear (one surface moving alonganother). rolling- element bearingsplain bearings2019. 03. 20. Hajdu Flóra

Plain Bearings works by sliding actionencompasses essentially all types other than rolling-element bearingsoften referred to as sleeve bearings or thrust bearings , terms that designate whether the bearing is loaded axially or radiallyLubrication is critical to the operation of plain bearings, so their application and function are also often referred to according to the type of lubrication principle used (hydrodynamic, fluid-film, hydrostatic, boundary lubricated, and self-lubricated) the largest number of bearings are oil-lubricated Hydrostatic : oil film is maintained through pumping by a pressurization system Hydrodynamic : oil film is maintained by a squeezing or wedging of lubricant produced by the rolling action of the bearing itself 2019. 03. 20. Hajdu Flóra

Plain Bearings - lubrication2019. 03. 20.Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Plain Bearings Sleeve (Journal) Bearing: cylindrical or ringshaped bearings designed to carry radial loadscast-bronze cylindrical bearings porous-bronze (powdered-metal) cylindrical bearings.Plastic bearings: resistance to abrasion, available in large sizes Thrust Bearings : differs from a sleeve bearing in that loads are supported axially rather than radially 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Bearing materials Babbitts:among the most widely used bearing materials. ability to embed dirtexcellent compatibility properties under boundary-lubrication conditions . Used as a thin coating over a steel strip i n bushings for small motors and in automotive engine bearings, For larger bearings in heavy-duty equipment, thick babbitt is cast on a rigid backing of steel or cast iron. Bronzes and Copper Alloys : Dozens of copper alloys are available as bearing materials. copper-lead, lead-bronze, tin-bronze, aluminum-bronze 2019. 03. 20. Hajdu Flóra

Bearing materials Aluminum:high wear resistance, load-carrying capacity,fatigue strength and thermal conductivity. excellent corrosion resistance inexpensive are used extensively in connecting rods and main bearings in internal-combustion engines; in hydraulic gear pumps, in oil-well pumping equipment, in roll-neck bearings in steel mills; and in reciprocating compressors and aircraft equipment.Porous Metals : Sintered-metal self-lubricating bearings ( powdered-metal bearings ) simple and low in cost. widely used in home appliances, small motors, machine tools, business machines, and farm and construction equipment. Plastics large variety of plastic materials. Many require no lubrication, high strength of modern plastics lends them to a variety of applications. 2019. 03. 20. Hajdu Flóra

Antifriction bearings 2019. 03. 20.Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Bearing loads Radial Load loads acting perpendicular to the axis of the bearing Radial bearings are designed primarily for straight radial service, they will withstand considerable thrust loads when deep ball tracks in the raceway are used. Thrust Load:Loads applied parallel to the axis of the bearing Thrust bearings are not designed to carry radial loads. Combination Radial and Thrust Loads When loads are exerted both parallel and perpendicular to the axis of the bearings, a combination radial and thrust bearing is used. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Ball Bearings Radialthrust, angular-contact: used for combined radial and thrust loads and where precise shaft location is needed .2019. 03. 20.Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Radial Bearings Deep-groove bearings the most widely used ball bearings. In addition to radial loads, they can carry substantial thrust loads at high speeds, in either direction. require careful alignment between shaft and housing. Self-aligning bearings 2 types: internal and external. In internal bearings, the outer-ring ball groove is ground as a spherical surface. Externally self-aligning bearings have a spherical surface on the outside of the outer ring that matches a concave spherical housing. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Radial Bearings Double-row, deep-groove bearings the same principle of design as single-row bearings. Can be used where high radial and thrust rigidity is needed and space is limited. about 60 to 80 % wider than comparable single-row, deep-groove bearings, and they have about 50 percent more radial capacity. Angular-contact thrust bearings can support a heavy thrust load in one direction, combined with a moderate radial load. High shoulders on the inner and outer rings provide steep contact angles for high-thrust capacity and axial rigidity. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Roller Bearings Types: cylindrical, needle, tapered, and spherical. Higher load capacities than ball bearings of the same sizeare widely used in heavy-duty, moderate-speed applications except for cylindrical bearings, they have lower speed capabilities than ball bearings2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Roller Bearings Cylindrical roller bearings high radial capacity and provide accurate guidance to th rollers. low friction - operation at high speedthrust loads of some magnitude can be carried through the flange-roller end contacts. Unlike ball bearings, cylindrical roller bearings are generally lubricated with oil - coolant. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Roller Bearings Tapered Bearingswidely used in roll-neck applications in rolling mills, transmissions, gear reducers, geared shafting, steering mechanisms, and machine-tool spindles. Low speeds: grease lubrication high speed: oil lubricationvery high speeds: special lubricating arrangements.Spherical Bearings unequaled combination of high load capacity, high tolerance to shock loads, and self aligning ability, but they are speed-limited. Single-row bearings most widely used a high radial capacity and a thrust capacity about 60 percent of radial capacity. Two-row bearings can replace two single-row bearings mounted back to back or face to face when the required capacity exceeds that of a single-row bearing. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Roller Bearings Needle BearingsRollers have high length-to-diameter ratios. Smaller rollers for a given bore size.Loose-needle bearings a full complement of needles in the annular space between two hardened machine components, which form the bearing raceways. effective and inexpensive bearing assembly with moderate speed capabilitysensitive to misalignment. Caged assemblies a roller complement with a retainer, placed between two hardened machine elements that act as raceways. Their speed capability is about 3 times higher than that of loose-needle bearings s maller complement of needles reduces load capacity Thrust bearings caged bearings with rollers assembled like the spokes of a wheel in a waferlike retainer. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Thrust bearings 2019. 03. 20.Hajdu Flóra

Bearing selection Ball bearings are normally the less expensive choice in the smaller sizes and lighter loads, whereas roller bearings are less expensive for the larger sizes and heavier loads. Roller bearings are more satisfactory under shock or impact loading than ball bearings.If there is misalignment between housing and shaft,either a self-aligning ball or a spherical roller bearing should be used. Ball thrust bearings should be subjected only to pure thrust loads. At high speeds, a deep-groove or angular contact ball bearing will usually be a better choice evenfor pure thrust loads. Self-aligning ball bearings and cylindrical roller bearings have very low friction coefficients. Deep-groove ball bearings are available with seals built into the bearings so that the bearing can be prelubricated and thus operate for long periods without attention 2019. 03. 20. Hajdu Flóra

Shaft and Housing FitsThe fit between the inner ring and the shaft and the fit between the outer ring and the housing must be suitable for the application fits can be obtained by selecting the proper tolerances for the shaft diameter and the housing bore. Bearings may be mounted dire c tly on the shaft or on tapered adapter sleeves. When the be ar ing is mounted directl y on the shaft, the inner ring should be located against a shaft shoulder of proper height. This shoulder must be machined square with the bearing seat, and a s h aft fillet should be used. The radius of the fillet must clear th e corner radius of the inner ring . This also applies when the outer ring is mounted in the housing. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Shaft and Housing Fits2019. 03. 20.Hajdu Flóra

Shaft and Housing FitsTo hold the bearing inner ring axially on the shaft, a locknut and lockwasher are commonly usedeffective and convenient methodA tab in the bore of the lockwasher engages a slot in theshaft, and one of the many tabs on the periphery of the washeris bent over into one of the slots in the nut 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Shaft and Housing FitsInstead of a nut, a retaining ring fitted into a groove inthe shaft can be used for simple bearing arrangements 2019. 03. 20.Hajdu Flóra

Shaft and Housing FitsIf another machine component (gear or pulley) is fitted alongside the bearing, the inner ring is often secured by means of a spacing sleeve. A sleeve is also frequently used for spacing the inner rings when the bearings are located reasonably close together. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Shaft and Housing FitsOn long standard shafting it is impractical to apply bearings, with an interference fit, directly on the shaft. they are applied with tapered adapter sleeves.The outer surface of the sleeve is tapered to match the tapered bore of the bearing inner ring. This will provide the required tight fit between the inner ring and the shaft. The adapter sleeve is slotted to permit easy contraction and is threaded at the smallend to fit a locknut. When the sleeve is drawn up tight between the bearing and the shaft, a press fit is provided at both the shaft and the inner ring. 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Shaft and Housing Fits2019. 03. 20.Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Shaft and Housing FitsOne of the most critical factors affecting bearing operation: the mounting fit of the bearing on the shaft and in the housing. If there is any clearance or looseness between the shaft and the bore of the inner ring, the shaft, as it rotates, will roll along the bore of the inner ring. The rolling shaft in the bearing bore will cause the shaft to wear rapidly andbecome progressively looser. The best way to prevent this rolling action and wear is to press-fit the inner ring on the shaft. Similar reasoning applies to a bearing subject to a load that rotates in space with the inner ring. Here, if the outer ring has a clearance in the housing bore, it will roll around the housing bore and wear loose. In this case it would be necessary to have the outer ring press-fit in the housing. In all cases, it is necessary to press-fit the bearing ring that has relative rotation with respect to the direction of the radial load. 2019. 03. 20. Hajdu Flóra

Seals for Grease LubricationFor ball or roller bearings to operate properly, they must beprotected against loss of lubricant and entrance of dirt and dust on the bearing surfaces. Simplest and least space-requiring form, this is accomplished in some types of bearings by the use of a thin steel shield on one or both sides of the bearing, fastened in a groove in the outer ring and reaching almost to the inner rings All other types of bearings require a seal between the bearing housing and the shaft 2019. 03. 20. Hajdu Flóra

Seals for Grease Lubrication2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Seals for Grease Lubrication2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Seals for Oil LubricationWith oil lubrication, seals have the double function of protecting the bearing against contamination and retaining thelubricant in the housing. Protection is obtained by means of friction seals or flingersThe essential feature for retaining the oil is a groove in therotating shaft, or a rotating ring or collar from whose edgesthe oil is thrown by centrifugal force. The oil-groove sea l retains the oil effectively but should be used only in dry and dust-free places where there is little danger of contamination labyrinth seals retain the oil and protect against contamination. 2019. 03. 20. Hajdu Flóra

Seals for Oil Lubrication2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Bearing Symbols 2019. 03. 20.Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Premounted Bearings Premounted bearing units consist of a bearing element anda housing, usually assembled to permit convenient adaptationto a machinery frame. All components are incorporated within a single unit to ensure proper protection, lubrication,and operation of the bearing. Both plain and rolling-element bearing units are available in a variety of housing designs and for a wide range of shaft sizes 2019. 03. 20. Hajdu Flóra Source : C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Premounted Bearings 2019. 03. 20.Hajdu Flóra Source: C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Premounted Bearings 2019. 03. 20.Hajdu Flóra Source: C. Jensen, J. D. Helsel , D. R. Short: Engineering Drawing&Design

Summary Bearings types Beairing mountsPreassembled bearing units Next week : Belts , chains , gears

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