ACTUATOR – MECHANICAL

FACULTY- SUSRI ANJANA SAHU

SEMESTAR- 5^TH MECHA ENGG.

SUBLECT- MECHATRONICS

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KINAMATIC LINK

It is defined as the part of machine which has a relative motion with respect to some other part of same machine is called Kinematic link or element.

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Rigid link- In this type of link there is no deformation while transmitting the motion. Motion between the piston and crank can be considered as a rigid link.

Flexible link- In this type of link there is partial deformation while transmitting the motion. Belt drive is an example of flexible link.

Fluid link- In this type of link the motion is transmitted with the help of fluid pressure. Hydraulic brake is an example of fluid link.

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KINEMATIC LINKS CAN BE DIVIDED INTO THREE TYPES.

KINEMATIC PAIRS

The two links or elements of a machine, when in contact with each other, are said to form a pair. If the relative motion between them is completely or successfully constrained (i.e. in a definite direction), the pair is known as kinematic pair. Let us discuss the various types of constrained motions.

TYPES OF KINEMATIC PAIRS

1. According to the type of relative motion between the elements.
2. According to the type of contact between the elements
3. According to the type of closure or mechanical connections

ACCORDING TO THE TYPE OF RELATIVE MOTION BETWEEN THE ELEMENTS �

• Sliding pair .
• Turning pair .
• Cylindrical pair .
• Rolling pair .
• Spherical pair.
• Helical pair or screw pair .

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• When the two elements of a pair are connected in such a way that one can only slide relative to the other, the pair is known as a sliding pair. The piston and cylinder, cross-head and guides of a reciprocating steam engine, ram and its guides in shaper, tail stock on the lathe bed etc. Are the examples of a sliding pair. A little consideration will show that a sliding pair has a completely constrained motion.

SLIDING PAIR

TURNING PAIR

• When the two elements of a pair are connected in such a way that one can only turn or revolve about a fixed axis of another link, the pair is known as turning pair. A shaft with collars at both ends fitted into a circular hole, the crankshaft in a journal bearing in an engine, lathe spindle supported in head stock, cycle wheels turning over their axles etc. are the examples of a turning pair. A turning pair also has a completely constrained motion

ROLLING PAIR

• When the two elements of a pair are connected in such a way that one rolls over another fixed link, the pair is known as rolling pair. Ball and roller bearings are examples of rolling pair.

SCREW PAIR

• When the two elements of a pair are connected in such a way that one element can turn about the other by screw threads, the pair is known as screw pair. The lead screw of a lathe with nut, and bolt with a nut are examples of a screw pair.

SPHERICAL PAIR

• When the two elements of a pair are connected in such a way that one element (with spherical shape) turns or swivels about the other fixed element, the pair formed is called a spherical pair. The ball and socket joint, attachment of a car mirror, pen stand etc., are the examples of a spherical pair

ACCORDING TO THE TYPE OF CONTACT BETWEEN THE ELEMENTS

• Lower pair
• Higher pair

LOWER PAIR

• When the two kinematic links are connected such that they have a surface contact between the two links it is called as lower pair.The joint by which two members are connected has surface contact.

HIGHER PAIR

• When the two kinematic links are connected such that they have a line or point contact between the two links it is called as higher pair

ACCORDING TO THE TYPE OF CLOSURE OR MECHANICAL CONNECTIONS

• Closed pair.
• Unclosed pair .

CLOSED PAIR

When the two elements of a pair are connected together mechanically in such away that only required kind of relative motion occurs, it is then known as self closed pair. The lower pairs are self closed pair

UNCLOSED PAIR

• When the two elements of a pair are not connected mechanically but are kept in contact by the action of external forces, the pair is said to be a unclosed pair. The cam and follower is an example of force closed pair, as it is kept in contact by the forces exerted by spring and gravity

MECHANISM

• When one of the link in a kinematic chain is fixed is known as mechaine .

SLIDER CRANK MACHANISM

• Slider-crank mechanism, arrangement of mechanical parts designed to convert straight-line motion to rotary motion, as in a reciprocating piston engine, or to convert rotary motion to straight-line motion, as in a reciprocating piston pump

TYPE OF SLIDING CRANK MACHANISM

• Pendulam pump.
• Oscilatery cylinder engine .
• Rotary IC engine .

PENDULAM PUMP

• The main importance of a pendulum pump is that the initiation energy for starting the process of pumping, swinging of the pendulum, is considerably minimum when compared with the work required to operate hand pumps.

OSCILATERING CYLINDER ENGINE

• A moving cylinder assembly includes a cylinder having a chamber for receiving and engaging a piston, and a housing immediately embracing the cylinder and defining a slot through which the piston is positioned to allow for oscillating

ROTARY IC ENGINE

• Rotary engine, internal-combustion engine in which the combustion chambers and cylinders rotate with the driven shaft around a fixed control shaft to which pistons are affixed; the gas pressures of combustion are used to rotate the shaft.

GARE DRIVE

• A mechanism consisting of toothed wheels that engage and transmit rotary motion, usually transforming angular velocity and torques. rack-and-gear drive is a special type of gear drive which transforms rotary motion into translatory motion or vice versa.

TYPE OF GARE DRIVE

• Spur gear .
• Bevel gear
• Helical gear
• Worm gear.

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SPUR GEAR

• A spur gear gear or pinion for transmitting motion between two parallel shaft.

BEVEL GEAR

Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well. The pitch surface of bevel gears is a cone.

HALICAL GEAR

Helical gears are one type of cylindrical gears with slanted tooth trace. Compared to spur gears, they have the larger contact ratio and excel in quietness and less vibration and able to transmit large force. A pair of helical gears has the same helix angle but the helix hand is opposite.

WORM GEAR

A worm gear is a gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel. ... It will typically take multiple reductions of a conventional gear set to achieve the same reduction level of a single worm gear - meaning users of worm gears have fewer moving parts and fewer places for failure.

BELT

A belt is a continuous band of flexible material passing over pulleys to transmit motion from one shaft to another .

TYPE OF BELT

• Flat belt
• V belt
• Round balt

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FLAT BELT

• Flat belts are usually made of leather, rubber and fabric. ... To achieve the desired thickness of belt, number of layers of belt material is cemented together. ` Usually the top and bottom layers are made of leather or rubber which has high coefficient of friction and also it acts as a protective layer.

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V-BELT

• A V-belt is a rubber belt used for driving mechanisms in an engine such as the fans 

ROUND BELT  

• Round belts are solid or hollow lengths of cylindrical material. They maintain contact with belt pulleys using friction and must be stretched or elongated to operate