Clutches And Brakes Regalpts Com-Free PDF

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Figure 2 Typical wet disc clutch brake, with multiple discs sively used in modern power trans. mission systems,ELECTROMAGNETIC,Three types of nonfriction electric. clutches and brakes are available,magnetic particle eddy current and. hysteresis Used primarily in applica,tions that require variable slip elec. tromagnetic clutches and brakes use,electromagnetic attraction rather.
than friction to perform their function,Magnetic particle. The operating principles of mag,netic particle clutches are illustrated. in Figure 6 The space between the in,put and output members is filled with. Figure 4 Drum type clutch a mixture of dry iron particles When. the coil is energized the magnetic, Figure 3 Caliper type disc brake flux lines span this space and line up. the particles on the magnetic flux, 4 have cylindrical friction surfaces slightly tapered and coaxial with the lines This results in the magnetic.
with a common axis the shaft on shaft and they are engaged in an ax particle chains locking the input and. which the unit is mounted Drum ial direction In this respect they are output members together causing. units are either constricting or ex a cross between drum and disc types them to rotate as a single unit The. panding types that is the drum is Cone clutches have light engage amount of particle bonding deter. contacted on either its outside or in ment forces and high power transmit mines the amount of torque that can. side diameter to force engagement ting capabilities but are difficult to be transmitted and is directly propor. Drum clutches and brakes wear disengage Cone units are not exten tional to the current flowing to the ro. evenly and transmit high torque The tor Torque can. contracting type responds especially therefore be ad. fast because centrifugal force helps justed by varying. withdraw the shoes rapidly thus the amount of cur, making them well suited for high rent flowing to the. cyclic operations coil Magnetic par,Cone clutches and brakes Figure 5 Figure 5. have friction surfaces that are Cone type clutch,A136 1997 Power Transmission Design. Hysteresis Figure 9 Square jaw clutch,These are con. stant torque devices consists of square teeth that lock into. that can be used to mating recesses in facing members It. Figure 6 Magnetic particle clutch provide any amount of slip as long as provides positive lockup but because. heat dissipation capacity of the unit is it cannot slip running engagement is. ticle clutches and brakes are useful in not exceeded Hysteresis losses trans limited to speeds under 10 rpm Sizes. tensioning and positioning applica mit torque in this type of clutch A coil accommodating from 1 to 260 hp per. tions where continuous changes of on the input rotor generates a mag 100 rpm are available. speed are required netic field in the rotor and drag cup. Figure 8 The hysteresis losses in the,drag cup cause the flux to change.
Spiral jaw, Eddy current more slowly through the cup than the Spiral jaw clutches use sloping en. Primarily used in variable speed rotor thus torque is transmitted gagement surfaces to overcome the. devices these clutches and brakes through the drag cup Hysteresis limited engagement speeds of square. cannot be operated at zero slip They brakes provide constant torque for a jaw types Though the smooth sloped. consist primarily of an input drum given control current Torque is inde engagement surfaces allow for en. stationary field coil and a coupling pendent of speed up to high speeds gagement speeds of up to 150 rpm. pole assembly that acts as an output Used primarily in fractional horse they can operate in only one direction. rotor Figure 7 When the field coil is power applications these brakes ex and have a tendency to freewheel. energized magnetic flux links the in hibit virtually no wear and almost un. put drum with the coupling pole as limited life,sembly Eddy currents developed. Multi tooth, when the input drum rotates create a These clutches offer the advan. new magnetic field that interacts, MECHANICAL LOCKUP tages of mechanical lockup clutches. with the field in the pole assembly A direct mechanical connection be combined with the advantages of elec. creating coupling torque proportional tween input and output components is tric pneumatic or hydraulic actua. to coil current used by mechanical lockup clutches to tion Running engagement speeds of. At zero slip the eddy current brake transmit torque Many use centrifugal up to 300 rpm are possible They are. has no torque thus it cannot be used force a wedging action or wrapping ac available in capacities to 300 hp per. where holding a load is required They tion to lock the input component to the 100 rpm Figure 10. are useful for providing drag loads output component and are often re. needed in applications such as ten ferred to as self activating types Speed. sioning difference in speed between input and, output members or The typical sprag type clutch has.
direction of rotation cylindrical inner and outer races. are used to engage with sprags filling the space in be. the torque transmit tween Figure 11 The sprags are. ting components An sized shaped and mounted in a man. other type of mechan ner that assures they will wedge be. ical lockup clutch the tween the two races when rotation oc. multi tooth design curs in the correct direction,uses electric pneu. matic or hydraulic,Wrap spring,In wrap spring clutches the input. shaft and output shaft are connected,Square jaw by a coiled spring whose inside diame. Figure 7 Eddy current Figure 8 Hysteresis clutch The square jaw ter is smaller than the outside diame. clutch clutch Figure 9 ter of the two shaft hubs Figure 12. 1997 Power Transmission Design A137, sleeve to the intermit ment Wear is greatly reduced by the. tently driven hub When oil film which lubricates while trans. the clutch is disengaged mitting most of the dynamic torque of. the roll cage forces the engagement, rolls down the ramps The heat of engagement is gener.
away from the sleeve ated in the oil film rather than on. Roll cage position is con working surfaces of the rotating ele. trolled by an external ments so the heat can be readily re. trip cam and trip lever moved and the drive s thermal capac. which may be actuated ity is high Also the oil absorbs the. manually or by electric shock of engagement as the film is. hydraulic or pneumatic squeezed between discs and plates. solenoid thus reducing drive train stress,Small diameter multiple disc designs. produce high torque to inertia ratios,OIL SHEAR These characteristics suit oil shear. CLUTCHES AND drives to applications ranging from,BRAKES high inertia to high cycle With ordinary. control logic drives handle 50 to 100 cy, Figure 10 Multi tooth clutch In a basic oil shear drive torque is cles min constant duty easily You can. transmitted through raise that significantly with various. shearing of an oil film valve and manifold arrangements. between two discs As Common applications include in. the rotating input disc dexing and reciprocating drives con. moves toward the sta veyors hoists shuttles packaging. tionary output disc the machines palletizers welders and. shearing allows the out machine tools Oil shear units serve in. put disc to begin rotat glass wood products steel automo. ing There is no friction tive textile building material food. material to metal packaging and other industries They. contact until input and are well suited for constant slip ten. output disc speeds are sion uses and adjustable speed drives. nearly equal Then the It can be shown that output torque. oil film breaks down al is directly proportional to viscosity. lowing full static engage relative surface velocity and area in. contact inversely proportional to oil,Figure 13 film thickness.
Roller ramp type clutch Clutch or brake output torque is. Figure 11 Sprag clutch proportional to the disc diameter as. well as contact area For a,given disc diameter you can. Rotation in one direction tightens the increase torque capacity by in. spring to transmit torque Rotation in creasing the number of discs. the opposite direction loosens the The modern oil shear clutch. spring and disengages the unit brake has 6 to 36 working sur. faces Actuation may be by,pneumatic hydraulic or,Roller ramp spring pressure. Roller ramp type clutches transmit Figure 14 shows such a. torque through rollers that ride on the clutch brake Compressed air. ramped surface of a hub Figure 13 or hydraulic fluid pressure in. When the clutch is engaged a roll troduced in the clutch makes. cage positions the the nonrotating centrally located pis. rolls at the top of ton exert clamping pressure on the. the ramps and clutch disc pack The pack consists of. torque is transmit steel discs drive plates keyed to the. ted from the con input shaft and alternate friction. tinuously rotating material faced discs splined to the. output shaft During acceleration,torque transfers from the input to the. output shaft through viscous shear in,Wrap spring clutch. the oil between friction surfaces,For braking compressed air hy.
A138 1997 Power Transmission Design,Brake pack,Clutch pack. Figure 15 In an oil shear unit oil flows, Figure 14 Typical oil shear clutch short as 50 milliseconds or as long as through the hollow barrel of clutch or brake. brake unit has multiple disc clutch and several minutes hub then to the friction discs Here the. brake packs Also the dynamic torque rating of clutch is engaged and fluid flows in the. brake stack in preparation for brake,an oil shear unit can be modified with. engagement, draulic fluid or springs force the pis different combinations of oil and fric. ton toward the brake end of the unit tion materials And because output. as air or hydraulic fluid exhausts torque varies inversely with film amount of drag is a function of viscos. from the clutch piston chamber The thickness control of clamping pres ity disc size relative slip speed and. piston clamps the brake disc pack sure allows easy control of torque running clearance Where residual. which is similar to the clutch pack ex In a drive with a speed reducer drag may be a problem steps can be. cept that the steel plates are keyed to load inertia referred to the drive is re taken to minimize it. the housing duced by the square of the reduction Most often oil shear drives are ap. For units that use external actua ratio There 50 or more of the motor plied in cycling applications where. tion of the brake light duty return output may go to accelerating the frequent stopping and starting can. springs are often used to move the drive 50 or more of the heat gener quickly burn up a dry friction unit or. piston In a spring applied safety ated comes from starting and stop make it lose positioning accuracy. brake setup heavy duty springs re ping the cyclic parts of the clutch Conversion to an oil shear drive is. place the light duty springs Loss of brake important in high cycling simplified because the self contained. electric power or actuating pressure work Because inertia increases by unit has its own bearings housing. automatically releases the clutch and the fourth power of diameter and and input and output shafts. sets the brake Clutch and brake torque increases proportionally to di Many oil shear drives serve con. overlap is mechanically impossible ameter or number of discs the small stant slip applications In start stop. Oil shear performance requires diameter multiple disc design can de uses the objective is to accelerate or. positive oil circulation through the liver high torque with minimum decelerate the load with full engage. disc packs Figure 15 to cool and lu inertia Drive rating increases almost ment of the clutch or brake But in. bricate friction surfaces and bearings in proportion to the number of work constant slip applications the objec. Typically transmission fluid is dis ing surfaces with no derating for tive is to slip continuously without. persed radially across the faces of the multiple disc construction You can full engagement Typical uses include. friction surfaces The fluid then flows get many torque ratings from one unwind brakes rewind clutches dy. to a sump where heat dissipates brake size by adjusting the number of namometer absorbers tension con. through the housing An internal wa discs and springs or adjusting clamp trol brakes constant tension drives. ter to oil heat exchanger can increase ing pressure and adjustable speed drives. thermal capacity The totally enclosed sealed hous Unwind brakes for example main. Not all wet clutches are oil shear ing prevents contamination from the tain fairly constant tension in a mate. units In some friction type drives oil outside Also normal maintenance re rial web even though the moment. may be used to cool the friction sur quires only maintaining oil level arm and thus the torque required. faces Unless the clutch brake main In general dynamic coefficient of changes as roll size diminishes. tains an oil film between surfaces it friction can vary even at seemingly Torque in the oil shear drive can be. behaves like a friction type clutch constant speed conditions and even controlled by manual adjustment of. brake Torque transfers mechanically more so with varying speed and tem clamping air pressure You can get ac. from one friction surface to another perature The coefficient for a . ticle clutches and brakes are useful in tensioning and positioning applica tions where continuous changes of speed are required Eddy current Primarily used in variable speed devices these clutches and brakes cannot be operated at zero slip They consist primarily of an input drum stationary field coil and a coupling pole assembly that acts

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