Abstract: Rocker mechanism. Practical use. Rocker mechanism: types, diagram, principle of operation The principle of operation of the mechanism

Rocker-yoke mechanism The rocker-yoke mechanism is a four-link lever mechanism, which includes a rocker and a rocker. This mechanism serves to convert the rocking motion of the input link (rocker arm or rocker). Rocker and rocker

Cam mechanism A cam mechanism is a mechanism that includes a cam. In various sectors of the industrial and economic complex of Russia, cam mechanisms in different versions are widely used. Option one: in the mechanism the cam has a working

Rocker mechanism Rocker mechanism is a lever mechanism that includes a rocker. In various machines, machine tools and other equipment, various types of rocker mechanisms are widely used: 1) rocker-slider mechanism; 2) crank-yoke

Mechanism A mechanism is a system consisting of several elements (or links) and designed to convert the movement of one or more solid elements into the required movements of other elements of the system. The mechanisms are characterized by: 1) mechanical

Lever mechanism A lever mechanism is a mechanism whose links form only rotational, translational, cylindrical and spherical pairs. An example of a lever mechanism is a cam-lever mechanism - a device that is a connection

Ratchet mechanism A ratchet mechanism is a device in which relative movement of the links is possible only in one direction, and in the other direction the links of such a mechanism interact due to the pressure of their elements and cannot move relative to each other

Lantern mechanism A lantern mechanism is a mechanism that has a lantern gearing in the form of gearing through cylindrical circular elements - lanterns and teeth with a mating profile. An example of a lantern mechanism is a lantern gear, in which

Hinge mechanism A hinge mechanism is a mechanism that has in its design one or more hinges in the form of links - rotating pairs. Hinge mechanisms are divided into: 1) two-link (the simplest); 2) three-link; 3) four-link. Four-link

Jump mechanism A jump mechanism is a device that provides periodic, intermittent movement of the film strip in the film channel during film projection or shooting and printing. A jump mechanism is a device for filming, film projection

Rocker mechanisms are designed to convert the rotational movement of the input link into the rotational movement of the output link. Usually in devices (RZG) they are used as intermediate converters between a lever transmission and a gear transmission.

CM with parallel axes sin type
b - distance between supports, R - length of the lever. 1-Slide 2-lever.	Conversion function: Circuit parameters:
CM with parallel axes sin type modified
	Conversion function: Circuit parameters:
KM with parallel axes tg type
	Conversion function: Circuit parameters:
KM with parallel axes tg type modified
	Conversion function: Circuit parameters:
Rocker PMs with intersecting axes These are spatial PMs. The axes are perpendicular and lie in the same plane. In the same plane, in the initial position, is the center of the contacting element - the SPHERE. The second contacting element plane is located in the initial position // of the plane of the mechanism axes. CM with intersecting sin-type axes
	Conversion function: Circuit parameters:
KM with intersecting axes tg type
	Conversion function: Circuit parameters:
Drive mechanisms The axes of drive mechanisms can intersect at an angle of 90º or different from it. The axes of the mechanism lie in parallel planes, spaced from each other at a distance equal to the sum of the radii of the contacting cylinders. Drive mechanism sin type
	Conversion function: Circuit parameters: If z =1, then x=0, does this mean the PT is linear???
Drive mechanism tg type
	Conversion function: Circuit parameters:

Design of Lever PMs.

What is the ERROR in the depiction of this mechanism???

LOCATION OF LINKS AND Gearbox does not meet the conditions of the initial position !!!

Lever shapeoften it turns out very complex(although these are flat parts!). This form is necessary to prevent paths from crossing LINKS and links touching the STAND during PM operationand at the same time minimize!!! Link weight.

In multi-link flat mechanisms, the links move in different planes. (See Fig.)

Static imbalance of PM links and its calculation

(For k/project)

The appearance of a moment from a static imbalance of the PM link is due to the fact that the center of mass of the link is not on the axis of rotation and thus, even in a stationary state, moments and forces arise in the mechanism due to the presence of gravity, which tend to rotate the links and create a force on the interconnected links.

This problem must be taken into account when designing links, choosing their configuration, materials and spatial arrangement in the device and machine.

The shape of links in the mechanisms of technical systems is very diverse: there are symmetrical parts and asymmetrical ones, in which c.t. does not lie on the axis of rotation.

In Fig. The design of a tangent-type rocker mechanism lever with parallel axes is shown.

Most of the bends and other apparent “excesses” of the form are due to the design of the entire assembled device (the parts should not touch each other, and at the same time be compact and light). However, the link design also plays a decisive role in terms of obtaining the unbalance moment.

KM link (lever) in two positions; a - 0º, b – 30º

Let's calculate the imbalance of this lever using the graphic-analytical method.

Let's divide the lever structure into 4 parts from top to bottom: the cylinder of the contacting element, the flat part of the lever body, the axial part of the lever, the eccentric of the sinus lever and the eccentric holder.

Let's find the centers of mass of the indicated parts of the structure (in this example, the solution was carried out using AutoCAD© (most “CAD drawings” have the ability to calculate mass-centering characteristics (MCC) of parts)). Let's find the approximate areas and volumes of these lever segments. The calculation results are shown in the table below.

As can be seen from the diagram, in this position (0 degrees) the link is quite well balanced - the sum of the moments is almost equal to zero, however, if the lever is tilted at an angle of 30º, the imbalance will change. For this position, the results are given in the table.

Introduction

1. Transmission mechanisms.

Literature

Introduction

SCENE (French coulisse), a link of the rocker mechanism, rotating around a fixed axis and forming a translational pair with another movable link (slider). Based on the type of movement, there are rotating, swinging, and rectilinear moving scenes.

ROCKET MECHANISM, a lever mechanism that includes a rocker.

Rocker mechanism, a hinge mechanism in which two moving links - the rocker and the rocker stone - are interconnected by a translational (sometimes rotational with an arc rocker) kinematic pair.

The most common flat four-link rocker mechanisms, depending on the type of the third moving link, are divided into groups: crank-rocker, rocker-rocker, rocker-slider, two-link. Crank-and-screw mechanisms can have a rotating, swinging or translational-moving link. Rocker-yoke mechanisms, obtained from the previous ones by limiting the angle of rotation of the crank, are made with a swinging (Fig. 1, a) and translationally moving (Fig. 1, b) rocker,

used to transform movement, and also as the so-called. sine mechanisms (Fig. 1, c) computing machines. Rocker-slider mechanisms are intended to convert rocking motion into translational motion or vice versa, and are also used as a tangent mechanism in computing machines. Two-stage mechanisms are used in machines (Fig. 2),

ensuring equality of the angular velocities of the wings at a constant angle between them. This property is used, for example, in couplings that allow displacement of the axes of the connected shafts. Complex multi-link rocker mechanisms are used for various purposes, for example, in systems for regulating the filling of cylinders of internal combustion engines, reversing mechanisms of steam engines, etc.

1.Transmission mechanisms

Gear mechanisms include planetary and crank mechanisms. These mechanisms allow complex movement.

In a planetary mechanism, rotational motion turns into planetary motion, in which the part rotates around its axis and at the same time around another axis (for example, this is how planets move in space - hence the name of the mechanism).

The planetary mechanism (Fig. 1.a) consists of two gears: driving 1, which is called solar, and driven 4, which is called satellite (there may be several of them). The necessary conditions for the operation of this mechanism are the rigid connection of these wheels using a lever - carrier 2, which gives movement to the satellite, and immobility of the sun wheel 3. The planetary mechanism can be made on the basis of two gears: gear (a, b) with external or internal gearing or chain (c). On the basis of a chain transmission, planetary motion can be transmitted over a greater distance than on a gear basis.

Rice. 2. Planetary mechanisms

The crank-rod (crank-slider, crank-rotary) mechanism serves to convert rotational motion into reciprocating motion (Fig. 2.). The mechanism consists of a leading member of the crank 1, which performs a rotational movement on the shaft, and a connecting rod 2, a slider 3 (b) or a slider, which performs a reciprocating movement. The connecting rod is connected using pin 4 to the working body - piston 3 (a). In Fig. 2.b shows a variant of the crank-slider mechanism, for example, in vegetable cutters.

Rice. 3. Crank-rod and crank-slider mechanisms

2. Front support (TU-4 aircraft landing gear)

The support is located in the forward part of the fuselage. The support niche is limited from above by the floor of the crew cabin, on the sides by longitudinal beams in the form of solid walls with belts along the top and bottom, in front and behind the niche is covered with solid walls of reinforced frames. The niche is closed from below by two side doors, hinged to the longitudinal beams.

The front support strut consists of a shock absorber, in the upper part of which a crossbar with two cylindrical axles on the sides is welded. Using these axles, the stand is hingedly suspended from two units installed on the side beams of the niche (Fig. 6)

The units are detachable and equipped with bronze bushings, to which lubricant is supplied from grease fittings. The trunnions fit into these bushings and are pressed against the body of the unit with caps on bolts. The housing of the wheel turning mechanism is rigidly fixed at the lower end of the shock absorber rod. Inside the housing, a spindle rotates on a roller bearing and a bronze bearing, to which the wheel axles are connected from below using an inclined pipe (Fig. 7.)

The wheels are mounted on these axles with their bearings and secured on the left and right with tightening nuts, followed by locking with cotter pins. When lateral loads are applied to the wheels, the spindle rotates in the mechanism body within the angles limited by stops on the body. The aircraft's turn on the ground is ensured by differential braking of the main gear wheels and free orientation in the direction of movement of the front gear wheels.

A bracket is attached to the front of the spindle, from which a special rod transmits the turning movement of the wheels to a hydraulic shimmy damper. The vane-type damper is bolted to the turning mechanism housing (Fig. 8.)

The spindle's thrust through the lever rotates the roller with movable blades and distils liquid from one cavity to another. Fluid resistance prevents the development of shimmy-type self-oscillations.

To set the wheels in a neutral position after the aircraft lifts off the ground, a spring-roller mechanism for setting the wheels in flight is mounted inside the spindle. It consists of a rocker hinged at the top of the spindle. A roller is installed at the outer end of the rocker, and its inner end, using a vertical rod, presses on a spring fixed in the spindle and having a pre-tension of about 4000 N (Fig. 9.)

Fig.7. Fig.8. Fig.9.

When the wheels turn, the spindle moves the rocker with the roller along the circumference forward or backward, forcing the roller to roll along a profiled cylindrical surface, which is fixed to the body of the turning mechanism. The profile is designed in such a way that any rotation of the wheels from the neutral position moves the roller upward and, compressing the spring, increases the force on the roller. In such a position deflected from neutral, the roller can only be supported by lateral loads on the wheels. After the aircraft takes off from the ground, these loads on the wheels disappear and the spring force forces the roller to roll to the lowest point of the profile, setting the wheels to a neutral position strictly in flight.

The strut shock absorber is liquid-gas plunger type with a needle. The cylinder and the shock absorber rod are connected to each other by a two-link link, which prevents the rod from turning in the cylinder.

In the extended position, the rack is held by the rear folding strut. The lower link of the strut is made in the form of a stamped fork, which is attached to the axles on the cylinder coupling. The upper link of the strut is a welded tubular frame, which is attached with its axles to two nodes on the side walls of the niche

The upper and lower links of the strut are connected to each other by a spatial hinge, consisting of an earring and two mutually perpendicular bolts (Fig. 10.) All strut axles are equipped with bronze bushings and lubricant from grease fittings. A screw lift is attached to the upper link of the strut, the second end of which is connected to the gearbox (Fig. 11.)

The bevel gear of the gearbox receives rotation from two independent electric drives, one of which is powered from the emergency network. The rotation of the gearbox gears is transmitted to a steel screw on which a bronze nut is installed (Fig. 12.)

Moving the nut along the axis of the screw with a steel pipe with a forked tip attached to the strut turns its upper link up when retracting and down when releasing the strut. Two blocks of limit switches are installed on the lift body, which turn off the drive in the extreme positions of the rack and ensure its reliable fixation due to the self-braking of the screw pair (Fig. 13.)

The niche doors open when released and close when the rack is removed. In the released position, the flaps are fixed by a rocker mechanism consisting of two hinged levers, the ends of which are attached to the flaps. In the open position of the shutters, the levers are locked with a spring-loaded stopper, which does not allow the levers to fold (Fig. 14.)

A cylindrical cam is fixed at the bottom of the shock absorber rod. At the end of cleaning the rack, the cam presses the stopper of the rocker mechanism and unlocks it. With further movement of the rack, the cam forces the levers to fold and turns the doors to close. In the retracted position of the rack, the cam, through levers, presses the doors to the edging of the niche and holds them in the closed position.

Literature:

1. Artobolevsky I. I., Mechanisms in modern technology, t, 1-2, M., 1970

2. Kozhevnikov S.N., Esipenko Ya.I., Raskin Ya.M., Mechanisms, 3rd ed., M., 1965;

Assembling the rocker mechanism

TO category:

Mechanical assembly works

Assembling the rocker mechanism

A type of crank mechanism is a rocker mechanism. Such mechanisms are used in cross-planing and slotting machines.

The rocker mechanism is shown in Fig. 1. The main part of the rocker mechanism is the rocker, which sits on an axis and swings relative to it. A crank disk is mounted behind the rocker, which has a radial groove in which the crank pin can move with the help of a screw driven by a roller through bevel gears. The disk with its shank sits in the wall of the frame and is driven into rotation by a gear wheel from the machine drive.

Rice. 1. The mechanism of the swinging link of the cross-planing machine

A stone (cracker) is placed on the finger, which fits into the longitudinal groove of the slide. When the crank disk rotates, the stone causes the rocker to swing around its axis, and itself moves along the groove of the rocker. The upper finger of the slide is freely connected to the machine slider and causes it to move back and forth along horizontal guides.

The advantage of the rocker mechanism is the high speed of the slider's reverse motion. This is especially important in machines where the return stroke is idle. But, on the other hand, the rocker mechanism can transmit significantly less force than the crank mechanism.

The parts of the rocker mechanism, i.e. the rocker, the crank disk, the stone are made of cast iron, the fingers, rollers, axles, gears are made of steel. The crank disk also serves as a flywheel.

The assembly of the rocker mechanism usually begins by connecting the crank disk to the liner through which the roller is passed. A bevel gear is installed on the end of the roller on the key. The screw is screwed into the hole of the crank pin, and at the other end of the screw, where there is no thread, a key is installed in the key socket. The bevel gear is then engaged with the gear wheel, which is adjusted by changing the thickness of the spacer rings or shims, and checked for paint by the spot where the tooth touches.

The lower end of the screw is inserted into the hole of the gear wheel, and then into the hole of the ledge. When the finger enters the groove of the crank disk, the screw is secured with a nut. The assembled disc shank assembly is then inserted into the hole in the frame. Then a bushing is put on the backstage axis, and the backstage is installed on it.

Next, a gear is installed on the axis on the key. A stone is inserted into the longitudinal groove of the slide and the assembled assembly unit is connected to the crank disk. In this case, the axis should fit into the corresponding hole in the frame, and the head of the slider should fit into the groove of the slider (the slider is not shown in the figure). After this, the finger is inserted into the hole of the stone and secured with a screw. The eccentric of the feed mechanism is placed on the end of the crank disk shank, and a lock nut is screwed onto the shaft thread.

After this, the rocker mechanism is adjusted by changing the stroke length of the slider by changing the radius of the crank pin (eccentricity). When the roller is rotated by a handle placed on its square end, through bevel gears, the screw moves the pin along the crank disk and changes the eccentricity. The greatest stroke length will be at the greatest eccentricity.

In a correctly assembled and installed machine, the guide scenes should be in a plane perpendicular to the axis. This axis should occupy a horizontal position, and the guide scenes should lie in a vertical plane. Their perpendicularity is checked with a frame level. In addition, the indicator checks the perpendicularity of the end of the crank disk of the axle.