Huang Research

8/8/2019 Huang Research

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Servo - Large

motor

motion actuator

rotation

A rotation is a moving thing a movement of anobject in a circular motion. An object rotates around acenter (or point) of rotation. A three-dimensional objectrotates always around an imaginary line called an axisas the Eulers rotation theorem shows. If the axis ofrotation is within the body, the body is said to rotateupon itself, or spinwhich implies relative speed andperhaps free-movement with angular momentum. Acircular motion about an external point.

CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.0CH.09


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Navigation by the Soles of Your Feet

vibration motor h t t p : / / w w w . s p a r

k f u n . c

o m / c o m m e r c e / p r o d u c

t_ i n f o

. p h p ? p r o

d u c t s_

i d = 8

4 4 9

h t t p : / / s p e c

t r u m . i e

e e . o

r g / r o b o t i c s /

h o m e - r o b o t s / n a v i g a t

i o n -

b y - t h e - s o

l e s -

o f - y o u r - f e e

t - a n d - t h e - s e a t - o

f - y o u r - p a n

t s e r s . a

s p

motion actuation:

vibration actuator

CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01

Description: A vibration motor! This itty-bitty,

shaftless vibratory motor is perfect for non-audible in-dicators. Use in any number of applications to indicateto the wearer when a status has changed. All movingparts are protected within the housing. With a 2-3.6Voperating range, these units shake crazily at 3V. Onceanchored to a PCB or within a pocket, the unit vibratessoftly but noticeably. This high quality unit comes with a3M adhesive backing and reinforced connection wires.


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stroke tubular actuator

Firgelli PQ Series with Position Feeback

motion actuation:

linear actuation

A linear actuator is an actuator that, whendriven by a non-linear motion, creates linear mo-tion (as opposed to rotary motion, e.g. of an electricmotor). Mechanical and hydraulic actuation are themost common methods of achieving the linear mo-tion.

Typically, a rotary driver (e.g. electric motor)is mechanically connected to a lead screw so thatthe rotation of the electric motor will make the leadscrew rotate. A lead screw has a continuous heli-cal thread machined on its circumference running

along the length (similar to the thread on a bolt).Threaded onto the lead screw is a lead nut withcorresponding helical threads. The nut is preventedfrom rotating with the lead screw (typically the nutinterlocks with a non-rotating part of the actuatorbody). Therefore, when the lead screw is rotated,the nut will be driven along the threads. The direc-tion of motion of the nut will depend on the direc-tion of rotation of the lead screw. By connectinglinkages to the nut, the motion can be converted

to usable linear displacement. Most current actua-tors are built either for high speed, high force, ora compromise between the two. When consideringan actuator for a particular application, the mostimportant speci cations are typically travel, speed,force, accuracy, and lifetime.

CH.09CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01


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hydraulic actuator

hydraulic actuator h t t p : / / w w w . a i r o

i l . c o m

/ p r o

d u c t s / v i e w

/ 4 9 8 / v r x - p n e u m a t

i c - r o

t a r y - a c t u a

t o r .

h t m

l

h t t p : / / w w w . s p

i r a x s a r c o . c

o m / r e s o u r c e s / s t e a m - e n g

i n e e r i n g -

t u t o r i a

l s /

c o n t r o

l - h a r

d w a r e - e l - p n - a c

t u a t

i o n / c o n t r o l - v a l v e - a c t u a

t o r s - a n d - p o s

i t i o n -

motion actuation:

hydraulic actuator


Hydraulic actuators or hydraulic cylinders typi-

cally involve a hollow cylinder having a piston insertedin it. The two sides of the piston are alternately pressur-ized/de-pressurized to achieve controlled precise lineardisplacement of the piston and in turn the entity con-nected to the piston. The physical linear displacementis only along the axis of the piston/cylinder. This designis based on the principles of hydraulics. A familiar ex-ample of a manually operated hydraulic actuator is ahydraulic car jack. Typically though, the term "hydraulicactuator" refers to a device controlled by a hydraulic

pump.


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typical piston actuators

typical piston actuators

motion actuator:

pneumatic actuator

Pneumatic actuators are powered by com-pressed air. They offer rapid point-to-point linearpositioning and have a high load-carrying capac-ity relative to their size; they are also cheap, me-chanically simple and easy to maintain.

Pneumatic systems are extensively used inindustry, where factories are commonly plumbedwith compressed air or other compressed inertgases. This is because a centrally-located andelectrically-powered compressor that powers cyl-inders and other pneumatic devices through sole-

noid valves is often able to provide motive powerin a cheaper, safer, more exible, and more reli-able way than a large number of electric motorsand actuators.

CH.01 CH.02 CH.03 CH.04 CH.05 CH.06 CH.07 CH.08 CH.09


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muscle wire rotate actuator

typical muscle wire

h t t p : / / w w w . a c

t i v e - r o

b o t s

. c o m

/ p r o d u c t s / m o t o r s a n d w h e e

l s / l i n e a r -

a c t u a t o r . s

h t m

l

h t t p : / / w w w .

j a m e c o . c o m

/ w e b a p p / w c s / s t o r e s

/ s e r v l e

t /

P r o d u c

t D i s p l a y ?

l a n g

I d = -

1 & s t o r e I

d = 1 0 0 0 1 & c a

t a l o g I

d = 1 0 0 0 1 & p a = 3

5 7 5 9 5

& p r o

d u c t

I d = 3

5 7 5 9 5 & k e y C o d e =

W S F & C I D = G M C

motion actuator:

muscle wire

A shape memory alloy (SMA, smart metal,memory metal, memory alloy, muscle wire, smartalloy) is an alloy that remembers its original, cold-forged shape: returning the pre-deformed shape byheating. This material is a lightweight, solid-state al-ternative to conventional actuators such as hydraulic,pneumatic, and motor-based systems. Shape memoryalloys have applications in industries including medi-cal and aerospace.

The three main types of shape memory alloysare the copper-zinc-aluminium-nickel, copper-alumin-

ium-nickel, and nickel-titanium (NiTi) alloys but SMAscan also be created by alloying zinc, copper, gold, andiron. NiTi alloys are generally more expensive andchange from austenite to martensite upon cooling; Mfis the temperature at which the transition to Martensiteis nished during cooling. Accordingly, during heatingAs and Af are the temperatures at which the trans-formation from Martensite to Austenite starts and n-ishes. Repeated use of the shape memory effect maylead to a shift of the characteristic transformation tem-

peratures (this effect is known as functional fatigue,as it is closely related with a change of microstructuraland functional properties of the material).



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memory alloy starter kits

Image Caption

motion actuator:

shape momory alloy


A shape memory alloy (SMA, smart metal,memory metal, memory alloy, muscle wire, smartalloy) is an alloy that "remembers" its original, cold-forged shape: returning the pre-deformed shape byheating. This material is a lightweight, solid-statealternative to conventional actuators such as hy-draulic, pneumatic, and motor-based systems.Shape memory alloys have applications in indus-tries including medical and aerospace.

The three main types of shape memory al-loys are the copper-zinc-aluminium-nickel, copper-aluminium-nickel, and nickel-titanium (NiTi) alloys

h t t p : / / w w w . a c

t i v e - r o

b o t s

. c o m

/ p r o d u c t s / m o t o r s a n d w h e e

l s / l i n e a r -

a c t u a t o r . s

h t m

l

h t t p : / / w w w . m

i d e . c o m

/ p r o

d u c t s / s m a_

k i t / s m a_ s t a r

t e r_

k i t . p

h p


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lego gears

gears connectionh t

t p : / / s c

i e n c e .

h o w s

t u f f w o r

k s . c

o m / t r a n s p o r t / e n g i n e s - e q u i p m e n

t / g e a r .

h t m

mechanics of movement:

gears


Gears are used in tons of mechanical devices.

They do several important jobs, but most important, theyprovide a gear reduction in motorized equipment. Thisis key because, often, a small motor spinning very fastcan provide enough power for a device, but not enoughtorque. For instance, an electric screwdriver has a verylarge gear reduction because it needs lots of torque toturn screws, bu t the motor only produces a small amountof torque at a high speed. With a gear reduction, the out-put speed can be reduced while the torque is increased.

Another thing gears do is adjust the direction of ro-tation. For instance, in the differential between the rearwheels of your car, the power is transmitted by a shaft thatruns down the center of the car, and the differential has toturn that power 90 degrees to apply it to the wheels.


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Ball Caster Omni-Directional Metal

Ball Caster Omni-Directional Metal h t t p : /

/ w w w . s

p a r k

f u n . c o m / c o m m e r c e

/ p r o

d u c t

_ i n f o .

R e l e v a n t w e

b s i t e o f

t h e p r o v

i d e r

R e l e v a n t y o u t u b e v i d e o w e

b a d d r e s s

Description: A metal caster used for omni-direc-tional robots.

Omni-what? Imagine a robot with the dual-motor gear box. The robot can pivot in one spot, butit must also allow the other wheels on the drive trainto move or slide during a turn. This caster allows therobot to rotate and pivot in all directions - omni-direc-tional - without the need for complex steering mecha-nisms.


mechanics of movement

GEARS


10/34

h t t p : / / s c

i e n c e .

h o w s

t u f f w o r

k s . c

o m / t r a n s p o r

t / e n g

i n e s - e q u

i p m e n

t / g e a r .

h t m

mechanics of movement

GEARS


On any gear, the ratio is determined by the dis-tances from the center of the gear to the point of con-tact. For instance, in a device with two gears, if onegear is twice the diameter of the other, the ratio wouldbe 2:1.

One of the most primitive types of gears wecould look at would be a wheel with wooden pegssticking out of it.

The problem with this type of gear is that thedistance from the center of each gear to the point ofcontact changes as the gears rotate. This means thatthe gear ratio changes as the gear turns, meaning thatthe output speed also changes. If you used a gear likethis in your car, it would be impossible to maintain aconstant speed -- you would be accelerating and de-celerating constantly.

Many modern gears use a special tooth pro lecalled an involute. This pro le has the very importantproperty of maintaining a constant speed ratio between

the two gears. Like the peg wheel above, the contactpoint moves; but the shape of the involute gear toothcompensates for this movement. See this section fordetails.

PEG WHEEL GEAR


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Image Caption


Spur gears are the most common type of gears.They have straight teeth, and are mounted on parallelshafts. Sometimes, many spur gears are used at onceto create very large gear reductions.

Spur gears are used in many devices that youcan see all over HowStuffWorks, like the electric screw-driver, dancing monster, oscillating sprinkler, windupalarm clock, washing machine and clothes dryer. Butyou wont nd many in your car.

This is because the spur gear can be really loud.Each time a gear tooth engages a tooth on the othergear, the teeth collide, and this impact makes a noise.It also increases the stress on the gear teeth.

To reduce the noise and stress in the gears,most of the gears in your car are helical.

SPUR GEAR


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helical gears

gekucak gears


Helical Gears

The teeth on helical gears are cut at an angle to theface of the gear. When two teeth on a helical gear systemengage, the contact starts at one end of the tooth andgradually spreads as the gears rotate, until the two teethare in full engagement.

This gradual engagement makes helical gears op-erate much more smoothly and quietly than spur gears.For this reason, helical gears are used in almost all cartransmissions.

Because of the angle of the teeth on helical gears,

they create a thrust load on the gear when they mesh. De-vices that use helical gears have bearings that can sup-port this thrust load.

One interesting thing about helical gears is thatif the angles of the gear teeth are correct, they can bemounted on perpendicular shafts, adjusting the rotationangle by 90 degrees.

chanics of movement:

gears


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bevel gears

bevel gears


Bevel GearsBevel gears are useful when the direction of a

shafts rotation needs to be changed. They are usuallymounted on shafts that are 90 degrees apart, but canbe designed to work at other angles as well.

The teeth on bevel gears can be straight, spiralor hypoid. Straight bevel gear teeth actually have thesame problem as straight spur gear teeth -- as eachtooth engages, it impacts the corresponding tooth allat once.

Just like with spur gears, the solution to thisproblem is to curve the gear teeth. These spiral teethengage just like helical teeth: the contact starts at oneend of the gear and progressively spreads across thewhole tooth.

On straight and spiral bevel gears, the shaftsmust be perpendicular to each other, but they mustalso be in the same plane. If you were to extend thetwo shafts past the gears, they would intersect. Thehypoid gear, on the other hand, can engage with theaxes in different planes.

This feature is used in many car differentials.The ring gear of the differential and the input pinion

gear are both hypoid. This allows the input pinion to bemounted lower than the axis of the ring gear. Figure 7shows the input pinion engaging the ring gear of thedifferential. Since the driveshaft of the car is connectedto the input pinion, this also lowers the driveshaft. Thismeans that the driveshaft doesnt intrude into the pas-senger compartment of the car as much, making moreroom for people and cargo.


gears

h t t p : / / s c

i e n c e .

h o w s

t u f f w o r

k s . c


t / e n g

i n e s - e q u

i p m e n

t / g e a r .

h t m

h t t p : / / s c

i e n c e .

h o w s

t u f f w o r

k s . c o m

/ t r a n s p o r

t / e n g

i n e s - e q u

i p m e n

t / g e a r .

h t m


14/34

worm gears


Worm GearsWorm gears are used when large gear reduc-

tions are needed. It is common for worm gears to havereductions of 20:1, and even up to 300:1 or greater.

Many worm gears have an interesting propertythat no other gear set has: the worm can easily turnthe gear, but the gear cannot turn the worm. This isbecause the angle on the worm is so shallow that whenthe gear tries to spin it, the friction between the gearand the worm holds the worm in place.

This feature is useful for machines such as con-veyor systems, in which the locking feature can act asa brake for the conveyor when the motor is not turn-ing. One other very interesting usage of worm gears isin the Torsen differential, which is used on some high-performance cars and trucks.


gears

h t t p : / / s c i e n c e .

h o w s

t u f f w o r

k s . c


t / e n g

i n e s - e q u

i p m e n

t / g e a r .

h t m


15/34


rotoary--liner

The rack and pinion is used to convert between rotaryand linear motion. The rack is the at, toothed part, the pinionis the gear. Rack and pinion can convert from rotary to linearof from linear to rotary.

The diameter of the gear determines the speed that therack moves as the pinion turns. Rack and pinions are com-monly used in the steering system of cars to convert the ro-tary motion of the steering wheel to the side to side motion inthe wheels.

Rack and pinion gears give a positive motion especial-ly compared to the friction drive of a wheel in tarmac. In therack and pinion railway a central rack between the two railsengages with a pinion on the engine allowing the train to bepulled up very steep slopes.


movement conversion

h t t p : / / w w w .

y i n g - p i g . c o . u

k / m e c

h a n i s m s /

p a g e s / c a m . h

t m l


16/34

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


Cams are used to convert rotary motion into reciprocat-ing motion. The motion created can be simple and regular orcomplex and irregular.

As the cam turns, driven by the circular motion, the camfollower traces the surface of the cam transmitting its motionto the required mechanism.


movement conversion

CH.07


17/34


Reciprocating motion is back and forth motion. In theexample to the left the reciprocating motion of the piston isconverted to the rotary motion in the crank.

Reciprocating motion is measured by its throw (thedistance between the two extremes of motion) and by its pe-riod (the length of time for each cycle)


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


18/34


Geneva Stop

The Geneva stop is named after the Geneva cross,a similar shape to the main part of the mechanism.

The Geneva stop is used to provide intermittent mo-tion, the orange wheel turns continuously, the dark blue pinthen turns the blue cross quarter of a turn for each revolu-tion of the drive wheel.

The crescent shaped cut out in dark orange sectionlets the points of the cross past, then locks the wheel inplace when it is stationary.

The Geneva stop mechanism is used commonly in lm projectors to move the lm on one frame at a time.


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


19/34


Irregular MotionIrregular motion is motion which has no obvious

pattern to its movement. It is often needed in automata torecreate the movements of living things.

Irregular motion is usually created using a cam orseries of cams

Irregular motion is not often used as the startingpoint for a mechanism. It can, however be translated andtransormed as shown below.


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


20/34


movement conversion


PulleysOn the left is a simple pulley. As the rope is

pulled down the weight moves up by the same dis-tance.

In the compound pulley on the right the ropeis wrapped around two pulleys. As the rope is pulledthe weight, this time attached to the lower pulley rath-er than direct to the rope, moves up slower than thespeed that the rope is pulled.

Corresponding to this reduction in speed is anincrease in the force on the weight.

The amount of increase in the force dependson how many times the rope wraps round the pulleys.By wrapping the rope several times around the pul-leys it is easily possible to lift your own weight off theground!

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


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Belt Drives

Belt drives are used transfer rotational mo-tion from one place to another.

On the left, both pulleys are the same size.Drive can be transfered by friction of the belt onthe pulley or, if required, buy using a toothed belt.Chain drives work in a similar way.

By crossing the belt the direction of drivecan be changed.

On the right two sizes of pulley are used toshow how speed of rotation can be changed.


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


22/34


Ratchet

The ratchet can be used to move a toothed wheelone tooth at a time. The part used to move the ratchet isknown as the pawl.

The ratchet can be used as a way of gearingdown motion. By its nature motion created by a ratchetis intermittent. By using two pawls simultaniously this in-termittent effect can be almost, but not quite, removed.

Ratchets are also used to ensure that motion

only occurs in only one direction, useful for windinggear which must not be allowed to drop. Ratchets arealso used in the freewheel mechanism of a bicycle.


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


23/34


Invented by Girolamo Cardano in the 16th centu-

ry the Cardan gear is a way of converting rotary motioninto straight line motion. Watch how the red dot on theinner purple gear exactly follows the vertical dotted line.

The outer gear has a diameter exactly twice aslarge as the inner gear. In the above example they have40 and 20 teeth respectively.

Cardano also invented a type of universal jointand investigated the mathematics of probability. Under-standing the mathematics of risk helped him make a liv-

ing from gambling until eventually he could

nd no-oneto gamble with and had to move onto new pastures...


movement conversion


24/34

Levers are an essential part of many mecha-nisms. They can be used to change the amount, thestrength and the direction of movement.

The position of the force and the load are inter-changeable and by moving them to different points onthe lever, different effects can be produced.

The xed point of the lever about which it movesis known as the fulcrum.

In this example the force and the load move inopposite directions.

With the force three times closer to the fulcrum

them the load lifted is only one third of the force but itmove three times as far.



movement conversion

h t t p : / / w w w .

y i n g - p

i g . c

o . u k

/ m e c

h a n i s m s /


t m l


25/34


Bell Crank The bell crank is used to convert the direction

of reciprocating movement. By varying the angle of thecrank piece it can be used to change the angle of move-ment from 1 degree to 180 degrees.

The bell crank was originally used in large houseto operate the servants bell, hence the name.


movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


26/34

Oscillating motion is motion which moves alonga path, then returns along that same path backwardsand forwards, backwards and forwards.

In this example the drive wheel is used to powera waving machine, notice how the left to right move-ment is slower than the right to left. This is becausethat left to right motion takes place over a longer partof the drive wheels turn.

By moving the drive wheel closer to the pivot

point this effect can be exaggerated. The same mech-anism is used in mechanical saws to provide a quickreturn after the cutting stroke.



movement conversion

h t t p : / / w w w .


k / m e c

h a n i s m s /


t m l


27/34


joints

ball joints are spherical bearings that connectthe control arms to the steering knuckles. More spe-cically, a ball joint is a steel bearing stud and socketenclosed in a steel casing. The bearing stud is taperedand threaded. It ts into a tapered hole in the steeringknuckle. A protective encasing prevents dirt from get-ting into the joint assembly. Motion control ball jointstend to be retained with an internal spring, which helpsto prevent vibration problems in the linkage. Common-ly found in automotive throttle linkages, throttle bodyset ups, these are also widely used on construction

equipment, the end of gas springs and in childrenstoys.



28/34


h t t p : / / w e

b . m

i t . e d u / m e c

h e n g

/ p m

l / s p e c

_ c o n

g .

h t m


joints

Revolute joint seen in 3-dimensional, notingthat the joint may only move in one direction.A revolute

joint (also called pin joint or hinge joint) is a one de-gree of freedom kinematic pair used in mechanisms.[1] Revolute joints provide single-axis rotation func-tion used in many places such as door hinges, foldingmechanisms, and other uni-axial rotation devices.


29/34


joints

This type of joint is also called a Hooke-typecoupling as it was developed from the joint inventedby Robert Hooke in the seventeenth century. This jointis commonly used today. The joints in Fig.A and B rep-resent the basic and developed forms respectively.They use two yokes set at 90 degrees to each otherand a cross-shaped trunnion block joins these yokes.


h t t p : / / w w w .

t h e - c r a n

k s h a f t . i n f o / 2 0 0 9 / 0 9 / u n i v e r s a l - j o

i n t s

. h t m l

h t t p : / / w w w .

t h e - c r a n

k s h a f t . i n f o / 2 0 0 9 / 0 9 / u n

i v e r s a l - j o

i n t s

. h t m l


30/34


echanics of movement:

joints

A prismatic joint (also called sliders) is a onedegree of freedom kinematic pair used in mecha-nisms.[1] Prismatic joints provide single-axis slidingfunction used in places such as hydraulic and pneu-matic cylinders.


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rezeppa joint

rzeppa joint

h t t p : / / w w w . m o t o m a x . p

l / e n g

/ d i v . D S

. h t m l

h t t p : / / w w w . e a r l m o r s e . o

r g / s t e a m

b o a t

i n g p a g e s / s t e a m

h a p p e n s 5

/ s t e a m -

h a p p e n s 5 . h

t m


joint

A Rzeppa joint consists of a spherical inner with6 grooves in it, and a similar enveloping outer shell.Each groove guides one ball. The input shaft ts in thecenter of a large, steel, star-shaped gear that nestsinside a circular cage. The cage is spherical but withends open, and it typically has six openings aroundthe perimeter. This cage and gear t into a groovedcup that has a splined and threaded shaft attached toit. Six large steel balls sit inside the cup grooves and t into the cage openings, nestled in the grooves ofthe star gear. The output shaft on the cup then runs

through the wheel bearing and is secured by the axlenut. This joint is extremely exible and can accom-modate the large changes of angle when the frontwheels are turned by the steering system; typical Rz-eppa joints allow 45-48 degrees of articulation, whilesome can give 52 degrees. At the outboard end ofthe driveshaft a slightly different unit is used. The endof the driveshaft is splined and ts into the outer joint.It is typically held in place by a circlip.



32/34

A cylindrical joint is a two degrees of freedomematic pair used in mechanisms.[1] Cylindricalnts provide single-axis sliding function as well as agle axis rotation, providing a way for two rigid bod-to translate and rotate freely. This can be picturedan unsecured axle mounted on a chassis, as it mayely rotate and translate.


h t t p : / / w w w .

t h e - c r a n

k s h a f t . i n f o / 2 0 0 9 / 0 9 / u n i v e r s a l - j o

i n t s

. h t m l

chanics of movement:

joints

1


33/34

The Thompson constant velocity joint

Image Caption

h t t p : / / w w w . c e n t r a

l w e s

t e r n

d a i l y

. c o m . a

u / n e w s

/ l o c a

l / n e w s / g e n e r a

l /

t h o m p s o n - i n - a - j o

i n t - v e n

t u r e - w

i t h - b o e

i n g /

1 3 7 3 8 2 5 . a s p x

h t t p : / / w w w .

t r a n g . c

o m . a

u / c o n c e p

t s . h

t m


research sub-topic

The Thompson constant velocity joint (TCVJ),also known as a Thompson coupling, is a constantvelocity universal joint that can be loaded axially andcontinue to maintain constant velocity over a rangeof input and output shaft angles with low friction andvibration. It consists of two cardan joints assembledwithin each other, thus eliminating the intermediateshaft, along with a control yoke that geometricallyconstrains their alignment. The control yoke maintainsequal joint angles between the input shafts and a rela-tive phase angle of zero to ensure constant angular

velocity at all input and output shaft angles. While thegeometric con guration does not maintain constantvelocity for the control yoke (aka intermediate cou-pling) that aligns the pair of cardan joints, the controlyoke has minimal inertia and generates virtually novibration. Eliminating the intermediate shaft and keep-ing the input shafts aligned in the homokinetic planevirtually eliminates the induced shear stresses andvibration inherent in traditional double cardan shafts.

The use of cardan joints within the ThompsonCoupling also reduces the wear, heat and frictionwhen compared with Rzeppa type constant velocity

joints. Cardan joints, including Thompson couplings,utilise roller bearings running circumferentially, where-as Rzeppa constant velocity joints use balls which rolland slide axially along grooves.



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A screw joint is a one degree of freedom kine-matic pair used in mechanisms.[1] Screw joints pro-vide single-axis translation by utilizing the threads ofthe threaded rod to provide such translation. This typeof joint is used primarily on most types of linear actua-tors and certain types of cartesian robots.

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