The intermittent motion mechanism can convert the continuous rotation of the driving member into the periodic motion and pause of the driven member, which is called the intermittent motion mechanism.
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For example, the lateral feed movement of the planer table, and the film feeding movement of the film projector all use intermittent motion mechanisms. Common intermittent motion mechanisms are: ratchet mechanism, sheave mechanism, link mechanism and incomplete gear mechanism.
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▲Intermittent movement of incomplete gears.
That is, if a gear that is not covered with the circumference is used as the driving wheel, a section of arc without teeth will not drive the driven wheel to rotate, and intermittent motion will be realized.
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▲Intermittent motion of the grooved wheel
A grooved sheave and a mechanism with round pins. When the round pin is inserted into the groove of the sheave, it drives the sheave to rotate, and when the round pin leaves the groove, the sheave stops rotating.
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universal joint
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The universal joint is a machine that realizes variable-angle power transmission. It is used for changing the direction of the transmission axis. It is the "joint" part of the universal transmission of the automobile drive system. The combination of universal joint and transmission shaft is called universal joint transmission.
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On vehicles with front-engine rear-wheel drive, the universal joint transmission device is installed between the output shaft of the transmission and the input shaft of the drive axle final drive; while the vehicle with front-engine front-wheel drive omits the drive shaft, the universal joint is installed Between the axle shaft of the front axle, which is responsible for both driving and steering, and the wheels.
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Cam type intermittent motion mechanism
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The cam type intermittent motion mechanism consists of a driving cam, a driven turntable and a frame. On the cylindrical surface of the driving cam there is a curved groove or raised ridge which is open at both ends and not closed, and on the end surface of the driven turntable there are evenly distributed cylindrical pins. When the cam rotates, the curved grooves or ridges move the cylindrical pins on the driven disc to make the driven disc move intermittently.
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rack and pinion drive
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The working principle of the rack and pinion is to convert the rotary motion of the gear into the reciprocating linear motion of the rack, or convert the reciprocating linear motion of the rack into the rotary motion of the gear.
The rack and pinion mechanism is composed of a gear and a rack. We have explained the gear in detail. Racks are divided into straight toothed racks and helical toothed racks. The tooth profile of the rack is a straight line instead of an involute (for the tooth surface, it is a plane), which is equivalent to a cylindrical gear with an infinite pitch circle radius.
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The main features of the rack:
(1) Since the rack tooth profile is a straight line, each point on the tooth profile has the same pressure angle, which is equal to the inclination angle of the tooth profile. This angle is called the tooth profile angle, and the standard value is 20°.
(2) Any straight line parallel to the addendum line has the same tooth pitch and modulus.
(3) The straight line parallel to the addendum line and the tooth thickness equal to the tooth space width is called the index line (center line), which is the reference line for calculating the rack size.
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belt drive
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Belt drive is a kind of mechanical transmission that utilizes a flexible belt tensioned on a pulley for motion or power transmission. According to different transmission principles, there are friction belt drives that rely on the friction between the belt and the pulley, and there are also synchronous belt drives that rely on the teeth on the belt and the pulley to mesh with each other.
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gear drive
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This structure is similar to a car differential, mainly composed of left and right side shaft gears, two planetary gears and a gear carrier.
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The power of the engine enters the differential through the transmission shaft, directly drives the planetary gear carrier, and then the planetary gear drives the left and right half shafts to drive the left and right wheels respectively. The design requirements of the differential meet: (rotational speed of the left half shaft)+(rotational speed of the right half shaft)=2(rotational speed of the planetary wheel carrier). When the car is going straight, the speeds of the left and right wheels and the planetary wheel carrier are equal and in a balanced state, but when the car turns, the balanced state of the three is destroyed, resulting in a decrease in the speed of the inner wheel and an increase in the speed of the outer wheel.
