Conventional designation of elements of kinematic schemes. Symbols of elements of kinematic schemes Conditionally graphic designation of a kinematic scheme

In order to schematically depict the main components of a machine or other mechanism, kinematic diagrams are used.

In such diagrams, nodes, details, ways of interaction of individual elements of the mechanism are depicted conditionally. Each type element has its own designation.

How to read kinematic diagrams of machine tools

In order to learn how to read kinematic diagrams, you need to know the designations of individual elements and learn to understand the interaction of individual components. First of all, we will study the most common designations of the most common elements, the symbols on the kinematic diagrams are presented in GOST 3462-52.

Shaft designation

The shaft on the kinematic diagram is indicated by a bold straight line. The spindle diagram shows the tip.

Designation of bearings in the diagrams

The designation of the bearing depends on its type.

Plain bearing depicted in the form of conventional brackets-supports. If the thrust bearing supports are depicted at an angle.

ball bearings on the kinematic diagrams of the machines are depicted as follows.

Balls in bearings are conventionally depicted as a circle.

In conditional images roller bearings the rollers are shown as rectangles.

Schematic designation of parts connections

Kinematic diagrams depict various types of shaft and component connections.

The symbol of the coupling depends on its type, the most common of them are:

• cam
• frictional

The designations of one-way couplings on the kinematic diagrams of the machines are shown in the figure.

The designation of a two-way coupling can be obtained by mirroring the one-way layout horizontally.

Designation of gears on machine diagrams

Gears are one of the most common elements of machine tools. The symbol allows you to understand what type of transmission is used - spur, helical, chevron, bevel, worm. In addition, according to the diagram, you can find out which wheel is larger and which is smaller.

Name	Designation	Name	Designation
Shaft		Gears:
Connection of two shafts:	cylindrical wheels
deaf
blind with overload protection		bevel wheels
elastic
articulated		screw wheels
telescopic
floating clutch		worm
gear clutch
Shaft connection:
free to rotate		rack
movable without rotation
with pull-out pin		Lead screw transmission with nut:
deaf		one-piece
Plain bearings:	detachable
radial		Couplings:
		cam one-sided
		cam double-sided
Rolling bearings:	conical one-sided
radial
angular contact one-sided		disk one-sided
double-ended angular contact		disc double-sided
Belt drives:	electromagnetic unilateral
flat belt
electromagnetic double-sided
overrunning unilateral
V-belt
overrunning double-sided
Brakes:
conical
chain transmission
shoe
disk

with wheel z6 it is necessary that the block freely passes by the wheel z8 without hitting it with a wheel z9. This is possible if z7 – z9 > 5. Otherwise, it is necessary to apply the transmission scheme shown in Fig. 2.15, b. On fig. 2.15, in brute force transmission is shown. Shaft I can receive rotation from the wheel z5 when turning on the cam clutch of the wheels z1 and z4. With the clutch disengaged and the wheel engaged z4 With z3 rotation on the shaft I is transmitted through gears z1/z2, shaft II and wheels z3/z4 .

Rice. 2.15. Gear box mechanisms: a─ with two

mobile blocks; b─ with a three-crown block;

in─ with enumeration; G─ with friction double-sided clutch

Transmissions with sliding blocks and dog clutches are simple in design, reliable in operation and easy to control, but do not allow switching during rotation and are large in the axial direction. On fig. 2.15, G a transmission is given that is devoid of these shortcomings. wheels z2 and z4 freely mounted on the shaft II and are constantly engaged with the wheels z1 and z3, rigidly fixed on the shaft I. The transfer of motion to the shaft II from the shaft I occurs when the friction double-sided clutch is turned on, which rigidly connects the wheels to the shaft II z2 and z4. In this case, the speed can be changed on the go.

In modern machine tools with automatic gearboxes, one and two-way friction electromagnetic clutches are used.

On fig. 2.16, a shows the mechanism of the meander with a captive wheel z0, which allows you to double the gear ratios when you turn on the adjacent pair of gears. If we accept shaft I as the leading one, and shaft II as the driven ones, and z \u003d z 2 \u003d z 3 \u003d z 6= 56, and z 1 = z 4 = z 5 = z 7= 28, then we get the gear ratios of the mechanism:

Rice. 2.16. Mechanisms meander feed boxes:

a ─ with a captive wheel; b ─ with a movable wheel

The meander mechanism is also called the “multiplying mechanism”. The cap wheel mechanism has the disadvantage that it does not provide a constant center distance between the cap wheel z0 and z2, since the swivel lever 2 is fixed with a non-rigid movable cylindrical latch 1.

On fig. 2.16 b a more perfect design of the meander mechanism is shown, from which the cap wheel with a swivel lever is excluded.

The connection with the wheels of the blocks is made by a movable wheel z, which ensures the constancy of the center distances.

Norton's mechanism (Fig. 2. 17) is a cone made up of gear wheels with a cap wheel mounted on a rotary lever with a cylindrical lock. Cap wheel z0 can alternately engage with all the wheels of the cone ( z1 – z6) and transfer motion from shaft I to shaft II. Thus, six different gear ratios can be obtained. The choice of the number of teeth of the cone wheels is not related to the constancy of the center distance between the driving and driven shafts. The advantage of this mechanism is compactness, the disadvantage is low rigidity. The main purpose of this mechanism is to create an arithmetic series of gear ratios. Mainly used in universal screw-cutting lathes.

Shown in fig. 2.15, a The scheme of a six-speed gear box is a conventional multiplier structure, consisting of one kinematic chain with a series connection of movable blocks (gear groups), and provides a geometric series of circular speeds of the output shaft. This structure allows you to successfully create rational drives of the main movement. However, in some cases, for example, in universal screw-cutting lathes, with an increase in the range of speed control, it is impossible to create a simple drive that meets the requirements on the basis of such a structure. Therefore, in the machine tool industry, so-called folded structures are used. Folded is the structure of a multi-speed stepped drive, consisting of two, less often three kinematic chains, each of which is a conventional multiplier structure. One of these circuits (short) is for higher drive speeds, the others (longer) for low speeds. As an example, in fig. 2.18 shows a diagram of a gear box for 12 spindle speeds (output shaft), which has a folded

In accordance with GOST 2.703 - 68 on the kinematic diagram, it is necessary to depict the entire set of kinematic elements and their connections, all kinematic connections between pairs, chains, etc., as well as connections with sources of motion.

The kinematic diagram of the product should be drawn, as a rule, in the form of a sweep. It is allowed to depict diagrams in axonometric projections and, without violating the clarity of the diagram, move elements up or down from their true position, as well as rotate them to positions that are most convenient for the image. In these cases, the conjugated links of the pair, drawn separately, should be connected by a dashed line.

All elements of the circuit must be depicted with conventional graphic symbols in accordance with GOST 2.770 - 68 (Fig. 10.1) or simplified external outlines.

The elements of the scheme should be depicted:

shafts, axles, rods, etc. - with solid main lines of thickness S;

elements depicted in simplified external outlines (gear wheels, worms, pulleys, sprockets, etc.) are solid thin lines with a thickness of S / 2;

the contour of the product, in which the circuit is inscribed, is in solid thin lines with a thickness of S / 3;

kinematic links between the mating links of the pair, drawn separately, - dashed lines with a thickness of S / 2;

the extreme positions of the element that changes its position during the operation of the product - thin dash-dotted lines with two points;

shafts or axles covered by other elements (invisible) - dashed lines.

Each kinematic element should be assigned a serial number, starting from the source of motion. The shafts are numbered in Roman numerals, the rest of the elements are numbered in Arabic. Elements of purchased or borrowed mechanisms (for example, gearboxes) are not numbered, a serial number is assigned to the entire mechanism.

The serial number is put down on the shelf of the leader line. Under the shelf, it is necessary to indicate the main characteristics and parameters of the kinematic element:

electric motor power, W and frequency of rotation of its shaft, min -1 (angular velocity, rad / s) or power and frequency of rotation of the input shaft of the unit;

torque, Nm, and speed, min -1 of the output shaft;

the number and angle of inclination of the teeth and the module of gears and worm wheels, and for the worm - the number of entries, the module and the diameter coefficient;

belt drive pulley diameters; number of sprocket teeth and chain pitch, etc.

If the diagram is overloaded with images of links and kinematic links, the characteristic of the elements of the diagram can be indicated on the drawing field - the diagram in the form of a table. It provides a complete list of constituent elements.

Let us explain some aspects of the process of reading and executing kinematic diagrams, and, first of all, with the accepted conventions when creating kinematic diagrams.

1. It is customary to depict the kinematic scheme in the form of a sweep. What does this word mean in relation to the kinematic scheme?

The fact is that the spatial arrangement of the kinematic links in the mechanism is for the most part such that it makes it difficult to depict them on the diagram, since the individual links obscure each other.

This, in turn, leads to misunderstandings or misconceptions about the schema. To avoid this, the schemes use the conditional method of the so-called expanded images.

On fig. 10.1, a picture of two pairs of gears is shown. Since it is customary to depict gears in the kinematic diagrams in the form of rectangles, it is easy to imagine that with a given spatial arrangement of gears, their images will overlap in pairs.

To prevent such overlays, regardless of the spatial arrangement of the kinematic links in the mechanism, it is customary to depict them in expanded form, that is, the rotation axes of all mating gears must lie in the same plane parallel to the image plane (see Fig. 10.1, b).

An example of a sweep of kinematic links in a diagram.

2. The transition from a constructive scheme to a kinematic one facilitates the figurative perception of the latter (Fig. 10.2). From this diagram it can be seen that the crank 1 has a rigid support, which is marked with a thick main line with hatching; piston 2, shown in the kinematic diagram in the form of a rectangle, has a gap with the cylinder walls, which, as fixed elements, also have one-sided shading. The gap indicates a possible reciprocating movement of the piston.

Structural and kinematic diagrams of an internal combustion engine

3. In all diagrams, shafts and axles are depicted with the same thick main line (Fig. 10.3). The difference between them is as follows:

a) the shaft supports are represented by two dashes with a gap on both shaft stops; since the shafts rotate together with the gear wheels (pulleys) mounted and connected to them with keys, the bearings are plain bearings or rolling bearings. In cases where it is necessary to clarify the type of shaft supports, the standard provides for special designations based on the given dashes;

b) the axis is a fixed product, therefore its ends are embedded in fixed supports, marked in the diagram by line segments with one-sided hatching. The gear wheel mounted on the axle rotates freely when the driven wheel rotates on the shaft.

Shafts and axles in kinematic diagrams

4. Some rules for reading kinematic diagrams:

a) for the most part, the drive gear (pulley) is the smaller of the mated pair, and the larger one is the driven one (Fig. 10.4). The letters n 1 and n 2 indicated in the diagram are the designation of the gear ratio or the ratio of the rotational speed n of the driving and driven wheels: n 1 / n 2;

Drive shaft and driven shaft on kinematic diagrams

b) in fig. 10.5 shows a reduction gear, since n 1 > n 2. In gearing, mating gears are made in one module, so the larger of the gears has more teeth. Gear ratio of the gear train:

where Z 1 and Z 2 - the number of teeth of the gears;

Reduction gear

c) in fig. 10.6 shows an overdrive, since n 1< n 2 ;

d) in fig. 10.7 shows three speed transmissions: a stepped pulley transmission with a flat belt and a gearbox with a movable block of gears.

In a belt drive, for the use of one belt at all stages, the following condition is provided: d 1 + d 2 \u003d d 3 + d 4 \u003d d 5 + d 6, where d 1, d 2, d 3, d 4, d 5, d 6 - pulley diameters in mm.

Rotation is transferred from shaft I to shaft II (n I and n II).

Rotation frequency:

n II \u003d n I d 1 /d 2; n II \u003d n I d 3 /d 4; n II \u003d n I d 5 /d 6.

Overdrive gear

Three speed gears

On fig. 10.7, b shows a gearbox for three speeds of rotation with a movable block of gears Z 1 - Z 3 - Z 5 that can move along the shaft key I; on shaft II, the wheels are rigidly connected to the shaft with keys.

Shaft speed II:

n II =n I Z 1 /Z 2 ; n II =n I Z 3 /Z 4 ; n II \u003d n I Z 5 / Z 6 .

where Z 1 , Z 2 , Z 3 , ..., Z 6 is the number of teeth of the wheels.

Since the gears of one module, then

Z 1 + Z 2 \u003d Z 3 + Z 4 \u003d Z 5 + Z 6.

5. It should be noted that the “scale-free” schemes are a relative sign. So, for basic kinematic diagrams, the ratio of the sizes of the conventional graphic symbols of the interacting elements in the diagram should approximately correspond to the actual ratio of the sizes of these elements.

This can be seen from the consideration of the principal kinematic diagrams of the conical differential gear hobbing machine, shown in orthogonal and axonometric projections (see Fig. 10.8). In these diagrams, the geometric dimensions of the bevel gears 3...6 are the same.

Kinematic circuit diagram of a bevel differential:

a – orthogonal projection; axonometric projection.

On fig. 10.9 shows an example of a schematic kinematic diagram, which consists of conditional graphic designations of elements, connections between them and alphanumeric positional designations of elements, as well as component elements of the circuit, made in the form of a table. The image can be used to represent the sequence of transmission of movement from the engine to the actuator. The table shows the designations of the constituent elements, their explanations and parameters.

Example of a kinematic circuit diagram

Designers who develop various machines and mechanisms often perform kinematic diagrams. At the same time, they are guided by the norms and requirements set forth in such a fundamental document as GOST 2.770–68.

Designation	Name
	Shaft, axle, rod, etc.
	Radial plain and rolling bearings on the shaft
	Thrust plain and rolling bearings on the shaft
	Plain bearings, radial
	Rolling bearings, radial
	Angular contact rolling bearings
	Coupling
	Coupling elastic
	Clutch (managed)
	Brake
	Flywheel on the shaft
	Ratchet gear mechanism with external gearing
	belt transmission
	chain transmission
	Cylindrical compression springs
	Tension springs, cylindrical
	Spur gears with external gearing
	Gear gears cylindrical with internal gearing
	Bevel gears with intersecting shafts
	Gears with cylindrical worm
	Rack and pinion gears
	Drum cams, cylindrical
	Rotating cams

In engineering, a diagram is a graphic image that shows the component parts of a product, their design features, as well as the links existing between them using simplified symbols and symbols. As part of the design documentation packages, diagrams play a rather important role. They are present both in general descriptions of products, instructions for their installation, adjustment and operation. Schematic drawings provide invaluable assistance to personnel involved in the installation, commissioning, repair of machines, mechanisms and individual units. Schemes make it possible to quickly understand what functional relationships exist between mechanical, hydraulic, electrical and other links and systems of technical devices.

When the development of a machine is just beginning, the designers draw a general outline of the future product by hand, that is, they draw up its initial scheme. It conditionally displays all the main nodes, and also shows the relationship between them. Only after the schematic diagram of the device has been worked out, the development of drawings and other design documentation begins.

In modern mechanical engineering, the greatest application is found by those machines in which the transmission of motion is based on the mechanical, hydraulic or electrical principle of operation.

purpose kinematic schemes is a reflection of the connection in which the working mechanism and the drive consist. It should be noted that in modern cars, machine tools and other technological equipment, mechanical transmissions are very complex and contain many elements. Therefore, in order to correctly create diagrams of such structures, you need to know perfectly well all the conventions that are used to graphically depict the principle of operation of a machine or mechanism without specifying their design features. For example, the kinematic diagrams of machine tools reflect exactly how the rotational movement of the motor shaft is communicated to the spindle, and the contour of the machine is shown (or not shown) with a thin line.

If non-standardized symbols are used on the diagrams, then they require explanation. As for the external outlines and schematic sections, they are depicted in the diagrams in a simplified way, in accordance with what kind of design each element of the product has.

On schematic images, leader lines are drawn from each of their component parts. From solid lines they start with arrows, and from planes - with dots. On the shelves of leader lines, the serial numbers of positions are indicated. At the same time, Roman numerals are used for elements such as shafts, and Arabic numerals for the rest. Under the shelves of leader lines, the parameters and main characteristics of the components of the circuits are indicated.

GOST 2.770-68*. ESKD. Conditional graphic designations in schemes. Elements of kinematics. Kinematic schemes symbols

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3 Kinematic diagrams of machine tools and symbols of their elements

The kinematic diagram of the machine is an image using symbols (table 1.2) of the relationship of individual elements and mechanisms, machines involved in the transmission of movements to various organs.

Table 1.2 - Symbols for kinematic diagrams GOST 2.770-68

Kinematic diagrams are drawn on an arbitrary scale. However, one should strive to fit the kinematic scheme into the contours of the main projection of the machine or its most important assembly units, trying to maintain their relative position.

For machine tools that, along with mechanical transmissions, have hydraulic, pneumatic and electrical devices, hydraulic, pneumatic, electrical and other circuits are also drawn up.

4 Determination of gear ratios and movements in various types of gears

The ratio of the speed (angular speed) n2 of the driven shaft to the speed n1 of the drive shaft is called the gear ratio:

Belting. Gear ratio excluding belt slip (Figure 1.1, a)

i = n2/ n1 = d1 / d2,

where d1 and d2 are the diameters of the driving and driven pulleys, respectively.

Belt slip is taken into account by entering a correction factor equal to 0.97-0.985.

Chain transmission. Gear ratio (Figure 1.1, b)

i = n2 / n1 = z1 / z2,

where z1 and z2 are the numbers of teeth of the driving and driven sprocket, respectively.

Gear transmission (Figure 1.1, c), carried out by cylindrical or bevel gears. gear ratio

i = n2 / n1 = z1 / z2,

where z1 and z2 are the numbers of teeth of the driving and driven gears, respectively.

Worm-gear. Gear ratio (Figure 1.1, d)

i = n2 / n1 = z / zk,

where Z is the number of worm visits; zk is the number of teeth of the worm wheel.

Rack transmission. The length of the rectilinear movement of the rack in one revolution of the rack and pinion gear (Figure 1.1, e)

where p = m - rack tooth pitch, mm; z is the number of teeth of the rack and pinion gear; m - rack and pinion tooth module, mm.

Screw and nut. Movement of the nut in one turn of the screw (Figure 1.1, e)

where Z is the number of screw starts; rp - screw pitch, mm.

5 GEAR RATIO OF KINEMATIC CHAINS. CALCULATION OF SPEED AND TORQUES

To determine the overall gear ratio of the kinematic chain (Figure 1.1, g), it is necessary to multiply the gear ratios of the individual gears included in this kinematic chain:

The speed of the last driven shaft is equal to the speed of the drive shaft multiplied by the total gear ratio of the kinematic chain:

n = 950 i total,

i.e. n = 950  59.4 min-1.

The torque on the Mshp spindle depends on the gear ratio of the kinematic chain from the electric motor to the spindle. If the electric motor develops the moment Mdv, then

Mshp = Mdv/ i total

where i total is the gear ratio of the kinematic chain from the electric motor to the spindle;  - efficiency of the kinematic chain from the electric motor to the spindle.

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Conditional graphic symbols on kinematic diagrams

Symbols used on kinematic diagrams are established by GOST 2.770 - 68.

Conditional graphic designations of elements of machines and mechanisms are given in table 1.1, the nature of movement in table 1.2.

Conditional graphic designations of elements of machines and mechanisms on kinematic diagrams

Conditional graphic designations of the nature of movement on kinematic diagrams

Name	Designation
Shaft, roller, axle, rod, connecting rod
Fixed link (rack). Note. To indicate the immobility of any link, a part of its contour is covered with hatching
Name	Designation
Connection of link parts:
motionless
fixed, adjustable
fixed connection of a part with a shaft, rod
Kinematic pair:
rotational
rotational multiple, e.g. double
progressive
screw
cylindrical
spherical with finger
universal joint
spherical (ball)
planar
tubular (ball-cylinder)
point (ball-plane)
Plain and rolling bearings on the shaft (no type specification):
radial
stubborn
Plain bearings:
radial
Name			Designation
persistent unilateral
persistent bilateral
Rolling bearings:
radial
radial-contact one-sided
double-ended angular contact
persistent unilateral
persistent bilateral
Coupling. General designation without type specification
Coupling non-disengaging (unmanaged)
deaf
elastic
compensatory
Coupling coupled (managed)
general designation
unilateral
bilateral
Mechanical clutch
synchronous, e.g. gear
asynchronous, for example, frictional
Electric clutch
Coupling hydraulic or pneumatic
Automatic clutch (self-acting)
general designation
overrunning (free wheeling)
centrifugal friction
safety with destructible element
Name			Designation
safety with indestructible element
Brake. General designation without type specification
Cams are flat:
longitudinal movement
rotating
rotating slot
Drum cams:
cylindrical
conical
curvilinear
Pusher (driven link)
pointed
arc
roller
flat
The link of lever mechanisms is two-element
crank, rocker, connecting rod
eccentric
creeper
Name			Designation
backstage
The link of lever mechanisms is three-element Notes: 1. It is allowed not to apply hatching. 2. The designation of a multi-element link is similar to a two- and three-element
Ratchet Gears:
with external gearing unilateral
with external gear double-sided
with internal gear unilateral
with rack and pinion
Maltese movements with radial grooves at the Maltese cross:
with external gear
with internal gear
general designation
Name			Designation
Friction gears:
with cylindrical rollers
with tapered rollers
with tapered rollers adjustable
with curvilinear generatrices of the working bodies and tilting rollers adjustable
end (frontal) adjustable
with spherical and conical (cylindrical) rollers adjustable
Name			Designation
with cylindrical rollers, converting rotational motion into translational
with hyperboloid rollers converting rotational motion into helical
with flexible rollers (wave)
Flywheel on the shaft
Stepped pulley mounted on the shaft
Belt transmission:
without specifying the type of belt
flat belt
V-belt
round belt
toothed belt
Chain transmission:
general designation without specifying the type of chain
round link
Name			Designation
lamellar
dentate
Gear transmissions (cylindrical):
external gearing (general designation without specifying the type of teeth)
the same, with straight, oblique and chevron teeth
internal gear
with non-circular wheels
Gear transmissions with flexible wheels (wave)
Gear transmissions with intersecting shafts and bevel:
Name			Notation
with straight, helical and circular teeth
Gear transmissions with crossed shafts:
hypoid
worm with cylindrical worm
worm globoid
Rack and pinion gears:
general designation without specifying the type of teeth
Transmission by gear sector without specifying the type of teeth
Screw that transmits motion
Nut on the screw that transmits the movement:
one-piece
one-piece with balls
Name			Designation
detachable
Springs:
cylindrical compressions
cylindrical tensions
conical compression
cylindrical, torsion
spiral
sheet:
Single
Spring
dish-shaped
shift lever
Shaft end for detachable handle
Lever
Handwheel
Mobile stops
Flexible Shaft for Torque Transmission

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GOST 2.770-68* - ESKD. Conditional graphic designations in schemes. Elements of kinematics.