Blind couplings. Due to the conditions of manufacturing, assembly and transportation, long shafts are sometimes made into composite shafts. In this case, the individual parts of the shaft are connected with blind couplings. In some cases, these couplings are used to ensure alignment of unit shafts.
A sleeve coupling (Fig. 10.1) is a sleeve that is fitted with clearance onto the ends of the shafts. The coupling has small diameter dimensions, but complicates installation due to the need for large axial displacements of the connected units. The material of the bushings is structural steel (art. 5, art. 3). Bush couplings are used to connect shafts with a diameter of up to 70 mm.
Flange couplings. A flange coupling (Fig. 10.2) consists of two identical coupling halves, made in the form of a hub with a flange. The flanges are connected with bolts. There are two designs:
1. Half of the bolts are installed in the flanges of the coupling halves without clearance. In this case, the centering of the coupling halves is carried out by these bolts. As a result of screwing the nuts, the flanges are pressed by the tightening forces of the bolts, and a frictional moment occurs at the ends of the flanges. The torque from one coupling half to the other is transmitted by bolt rods placed without clearance and by friction forces on the flanges.
2. All bolts in the flanges of the coupling halves are installed with clearance. At the same time, not
It is necessary to provide for the centering of the coupling halves. In this case, the entire torque from one coupling half to the other is transmitted by friction forces on the flanges.
Compensating couplings.
For economic and technological reasons, machines are usually made from separate units (assemblies) that are connected by couplings. However, accurate installation of the shafts of such units is impossible due to: manufacturing and installation errors; installation of units on a deformable (non-rigid) base; misalignment of the shafts as a result of thermal deformations of the housings of the units during their operation, as well as due to elastic deformations of the shafts under load.
Compensating couplings are used to connect shafts with divergent axes. Due to their design, these couplings ensure the operation of the machine even with mutual displacement of the shafts.
Gear couplings.
A double gear coupling (Fig. 10.3) consists of two identical hubs 1 (bushings) with external gear rims and two identical hubs 2 with internal gear rims. The cages are tightened with 3 bolts evenly spaced around the circumference. In the covers 4, which cover the internal cavity of the coupling, there are special rubber seals that hold the liquid lubricant inside the coupling. Plug 5 is used to fill the clutch with oil. Belts 6 on the bushings are used to control the alignment of the shafts, and threaded holes are used to fasten the indicator posts. The number of teeth and their sizes are selected so that the teeth of the bushing rim are located with some clearance between the teeth of the cage, forming gear connections.
To reduce the wear rate of teeth, blanks of bushings and cages are made forged or cast (for large sizes). Forged blanks are made from steel grades 35ХМ, 40, 45, and cast ones from steel grades 40Л, 45Л. The hardness of the surfaces of the teeth of the bushings and cages should be 42 - 50 HRC e.
Articulated couplings. Articulated couplings use the principle of operation of the Hooke's joint. These couplings are used to transmit torque between shafts with large skew angles up to 40-45°, which change during operation.
The coupling (Fig. 10.4) consists of two identical coupling halves in the form of a hub with a fork (the forks of the coupling halves are rotated 90°) and a cross connecting the coupling halves. The crosspiece is connected to the forks of the coupling halves by hinges. This ensures freedom of rotation of each coupling half relative to the crosspiece.
Elastic couplings.
Elastic couplings are distinguished by the presence of an elastic element and are universal in the sense that, having some torsional compliance, these couplings are also compensating.
Flexible couplings are capable of:
· soften shocks and shocks of torque caused by the technological process or the choice of clearance when starting and stopping the machine. In this case, the kinetic energy of the impact is accumulated by the coupling during the deformation of the elastic element, turning into potential deformation energy.
· protect the machine drive from harmful torsional vibrations;
· connect shafts that have mutual displacements. In this case, the deformation
the elastic element of the coupling is removed, and the coupling functions as a compensating one.
Couplings with non-metallic (rubber) elastic elements. Up-
Other couplings with rubber-cord and rubber elastic elements receive
They are very widespread due to their simplicity of design, low cost of manufacture, ease of operation (do not require maintenance), high torsional compliance and good damping ability. The last two important properties are determined by the properties of the rubber from which the elastic element of the coupling is made.
An elastic bush-pin coupling is shown in Fig. 10.5.
The elastic elements are rubber-cord bushings fitted onto the connecting pins.
An elastic coupling with a rubber star is shown in Fig. 10.6
In Fig. 10.7 is shown coupling with elastic element
in the form of an internal torus. Two identical coupling halves 2 are connected by a toroidal elastic element 1, the edges of which are pressed against the coupling halves by pressure rings 3 and screws 4, evenly spaced around the circumference.
Coupling with rubber conical washer
shown in Fig. 10.8. The rubber-metal elastic element 6 is attached to the coupling halves 1 and 2 with screws 5 evenly spaced around the circumference. Modern methods of vulcanizing rubber to metal make it possible to obtain a bond strength no lower than the strength of the rubber itself. The coupling does not have high compensating properties. However, it is successfully used in machine drives to dampen harmful torsional vibrations. By changing the angle of the cone, you can obtain the required torsional rigidity of the coupling.
In Fig. Figure 10.9 shows a coupling with elastic elements in the form of steel rods that bend under the action of a torque.
The coupling halves 1 and 7 are connected by cylindrical steel rods (springs) 5, evenly spaced around the circumference. Cover 3 and casing 4 keep the rods from falling out and retain the lubricant in the coupling thanks to seals 2 and 8. To reduce wear on the springs and their seats, the coupling is filled with oil with anti-seize additives through oiler 6.
The coupling halves are made of steel 45, 40Х, the rods are made of high-alloy spring steels, the covers and casings are made of cast iron Sch12.
Mechanical couplings
Couplings that can be used to easily separate shafts (often during operation) are called clutch couplings. Such couplings include form-fitting couplings and couplings.
Coupling couplings with geometric locking. Form-fitting couplings are classified according to the shape of the engaging elements.
A coupling with rectangular teeth (Fig. 10.10, a) can transmit torque in both directions. Its left part is rigidly attached (with a key) to the shaft. The right part is attached to the other shaft by a sliding key and is engaged or disengaged with the left part by moving the lever in the groove. The main disadvantage of such a clutch is the difficulty of clutching. A gear coupling, which engages more easily, but transmits torque only in one direction, is shown in Fig. 10.10, b.
The material of the jaw couplings must ensure high hardness of the working surfaces of the jaws. The following steel grades are used: 20Х, 12ХН3А with carburization and hardening to a hardness of 54 – 60 HRs. For frequent inclusions, steels are used: 40Х, 40ХН, 35ХГСА with hardening of the working surfaces of the teeth to a hardness of 40 - 45 HRs.
Freewheels
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These couplings serve to transmit torque in one direction only, when the angular velocities of the driving and driven coupling halves are equal. If the angular velocity of the driven half-clutch exceeds the angular velocity of the driving half, the clutch will automatically disconnect the connected units.
Roller freewheel shown in Fig. 10.11. The coupling consists of a cage 1 and a sprocket 2, which are half-couplings, rollers 3, evenly spaced around the circumference, and clamping devices consisting of a piston and a spring 7. The rollers hold the side covers 4, which secure the spring rings. The cage is kept from turning by a key 5. The driving link of the coupling can be either a sprocket or a cage. When the cage begins to overtake the sprocket, the roller by frictional forces against the sprocket and the cage moves to a wider part of the wedge gap and the coupling halves open.
Torque clutches
In Fig. Figure 10.12 shows a friction clutch used in crane rotation mechanisms and rotary winches. This coupling is also a connecting coupling. It connects the electric motor shaft to the gearbox. The clutch is equipped with a brake pulley; the engine is connected to the mechanism through discs. Some of the disks are fixed through splines on a sleeve rigidly connected to the gearbox shaft, the other part of the disks is fixed to the disk. Rigidly connected to the electric motor. The disks are pressed against each other by a constant force developed by compressed springs. The amount of compression of the springs, which determines the amount of torque transmitted by the clutch, is regulated by a threaded ring.
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10.2. Bearings
Bearings are the most common parts in mechanical engineering. Not-
It is possible to imagine any modern mechanism without a bearing, the functions of which are, on the one hand, to significantly reduce friction between the rotating and stationary parts of the mechanism, and on the other, to be able to bear a certain load. The seal also plays an important role, as it protects the bearing from external influences and retains the lubricant.
The durability and reliability of any mechanism largely depends on the correct choice and quality of the bearings, seals and lubricants used. Bearings, based on the type of parts used in them and their interaction during operation, are divided into rolling bearings and plain bearings. The most common are rolling bearings, which in turn are classified according to the direction of the perceived load relative to the shaft (radial, angular contact, thrust radial and thrust); shape of rolling bodies: ball, roller; number of rolling elements: single-row, double-row, etc. (see Table 10.1).
| Table 10.1 | ||||||
| Roller bearings | ||||||
| Characteristic | View | Characteristic | View | |||
| Single row radial roller bearing |  | Radial spherical single row bearing |  |
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| Double row radial roller bearing |  | Double row spherical radial roller bearing |  |
|||
| Angular contact roller bearing |  | Spherical thrust roller bearing |  |
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| Continuation of Table 10.1 | ||||||
| Tapered roller bearing |  | Thrust radial roller bearing |  |
|||
| Ball bearings | ||||||
| Single row deep groove ball bearing |  | Double row spherical radial ball bearing |  |
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| Split deep groove ball bearing |  | Single row thrust ball bearing |  |
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| Angular contact ball bearing |  | Double thrust ball bearing |  |
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| Double row angular contact ball bearing |  | Thrust radial ball bearing |  |
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| Needle bearings | ||||||
| Needle bearing with cage without rings |  | Double row needle bearing |  |
|||
| Double row needle bearing with cage without rings |  | Needle bearing with stamped outer ring and open end |  |
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| Single row needle bearing |  | Needle bearing with stamped outer ring and closed end |  |
|||
| End of table. 10.1 | ||||||
| Combined bearings | ||||||
| Combined bearing (radial needle and angular contact ball) |  |  | Combined bearing (radial needle | |||
| Housing bearings |  |
|||||
Fastening connections
In mechanical engineering, four main types of threaded fastening connections are used: bolts with nuts (Fig. 10.13, a), screw bolts (screws) (Fig. 10.13, b ), studs (Fig. 10.13, V ) intermediate (Fig. 10.13, G).
1. Connection with bolts is applicable only if it is possible to make through holes in the mating parts.
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2. Connections with screw-in bolts are used for blind threaded holes (Fig. 10.13, d), when it is impossible to use a bolt with a nut, or for a through threaded hole, when it is possible to install a bolt on only one side of the connection.
Parts with threaded holes are made of steel, malleable and high-strength cast iron, titanium alloy, bronze. Parts made of soft alloys (aluminum, magnesium, zinc, etc.) require the use of intermediate threaded bushings made of a harder metal.
3. Connection with studs is used for parts made of soft (aluminum and magnesium alloys) or brittle (gray cast iron) materials, as well as for blind or through threaded holes in cases where frequent unscrewing of the studs is undesirable.
4. In addition to the main types of connections described, intermediate ones are also used. These include, for example, the connection used, shown in Fig. 10.13, and . The bolt is secured with a nut in a smooth hole in one part; the other part is tightened with a nut screwed onto the free end of the bolt.
General purpose fasteners are most often made from steel 35, critical parts (connecting rod bolts, power studs, etc.) are made from chromium steels type 40X, chromansil type 30HGS, heat-resistant steels type 30ХМ, 50ХФА, 25Х12М1Ф, from corrosion-resistant steels type 30Х13, 40Х13.
In serial and mass production, threads are cut using whirlwind cutting and milling methods. The most productive and at the same time providing the highest thread strength is the thread rolling method.
Industry Standards
They are compiled for products used only in a certain industry.
Each machine-building plant or group of plants in any industry has its own standards and norms. These are technical documents that prescribe the use of only certain metal profiles, die sizes, and processing methods. They also establish the dimensions of fasteners: nuts, bolts, washers, etc. And when the designer develops a machine, he is obliged to adhere to the standards and norms that are accepted at the manufacturing plants. The more standard instruments, devices and parts there are in a new machine, the simpler the machine is to manufacture and more reliable in operation. After all, such parts are produced in large quantities, and therefore they are cheaper, they can be easily replaced if damaged.
State and industry standards regulate the technical data of products, mandatory types and methods of their testing and verification. The manufacturer is obliged to strictly observe all this and has no right to produce products that deviate from GOST or OST.
There are no standards developed for products that are produced in small quantities. Instead, factories draw up technical specifications, which also determine all product indicators and are strictly observed by manufacturers.
In cases where state standards cover a group of machines for the same purpose at once, separate technical specifications are also drawn up for each individual type of machine to clarify the standard.
Possible methods of connecting the engine and cylindrical, bevel-helical, and worm gearboxes are presented in Fig. 2.1, where a, d, i are shaft-to-shaft connections, b, f, j are connections with a compensating clutch, c, g, l are gear connections, g, h, m are V-belt connections.
The “shaft to shaft” connection is used: when trying to reduce overall dimensions and weight; if a rigid connection is necessary to obtain precise positioning and precise speed of movement; while striving to reduce the reduced moment of inertia
drive. This connection is compact, but extremely sensitive to errors in the manufacture and assembly of the drive. As these errors increase, the forces in the supports of the connected shafts of the engine and gearbox increase, and the possibility of fretting in the connection arises. As is known, fretting of fixed joints
is a type of damage that occurs when two surfaces that are in contact and nominally stationary in relation to each other experience local small periodic relative displacements.
When connecting the motor and gearbox shafts using a compensating clutch, it is possible to compensate for fairly large errors in the drive assembly. In this case, the length of the drive increases slightly. The cantilever radial load on the connected shafts is approximately 0.2 of the circumferential force on the coupling.
If the shafts of the motor and gearbox are connected by a gear, then the overall size of the worm or bevel geared motor increases slightly in length. In this case, the gear motor becomes, respectively, a cylindrical-worm or a cylindrical-bevel-cylindrical. The connected shafts are loaded by forces acting on the gear teeth.
The connection using a V-belt drive increases the overall size of the gearmotor in height. The load on the connected shafts is determined by the cantilever radial pre-tensioning force of the belts.
Comparative analysis (Fig. 2.2) of the prevalence of various motor shaft connections and
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
gearboxes in geared motors for general industrial use from 72 companies in 17 countries showed that three types of connections: “shaft to shaft” (white fill), compensating coupling (black fill), using a gear drive (gray fill) are quite common in modern motors. gearboxes manufactured both in Western countries and in Russia. Belt drive connections were not included in this analysis, since they are used only by some gearmotor manufacturers.
The “shaft to shaft” connection is used by Bockwoldt (Germany) in a cylindrical-bevel-helical gearmotor. The companies Rotor (Netherlands), Renold (Great Britain), Innovari (Italy) use such a connection in one-, two- and three-stage helical gear motor gearboxes. Coupling connection is typical
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
for gearmotors from Stöber, Bauer (Germany), etc. It is performed using a gear coupling, sprocket coupling, MUVP, etc. The connection of gears is common in Germany (SEW, Bauer, Nord), Great Britain (Renold), USA (Baldor Dodge company), Italy (Innovari, Rossi companies) and other countries.
2.1 Shaft-to-shaft connection
IN geared motors Three types of “shaft to shaft” connections are used: 1) both the motor shaft and the gearbox shaft are mounted on two supports, the torque is transmitted by a keyed connection; 2) both the motor shaft and the gearbox shaft are mounted on two supports, the torque is transmitted by short splines; 3) the motor shaft is mounted on two supports, and the input shaft of the gearbox is mounted on one, the torque is transmitted by a tension connection created by tightening the screws of the terminal connection.
In Fig. 2.3 shows these types of connections in relation to a helical-bevel-helical geared motor: the first (a) is a geared motor from Pujol Muntala (Spain); second (b) – gear motor from ZAE (Germany); the third (c) is a gear motor from Bauer (Germany). The first type of connection is also used by companies
GFC and Bockwoldt (Germany), Renold (UK), Rossi
(Italy), Mozhga-Reductor LLC, Reductor OJSC, Barysh, Reductor OJSC, Izhevsk (Russia), etc. The second type of connection is also common among Swedrive (Sweden), Bonfiglioli (Italy) ) etc. The third type of connection is also used by KEB (Great Britain) and others.
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
An example of a connection of the third type in relation to a planetary gearmotor from ZF (Germany) is shown in Fig. 2.4 (the engine is not shown in the figure).
As is known, a rod fixed in one support (Fig. 2.5, a) forms a mechanism. To fix the rod in space, it is enough to install it on two supports (Fig. 2.5, b). If the number of supports is increased, then the system becomes statically indeterminate and to determine the reactions in the supports it is necessary, in addition to the equilibrium equations, to formulate conditions for the compatibility of movements. When the shafts are misaligned or misaligned, the supports located near the connection are loaded with forces that can exceed the reactions in the supports from the work process. A four-bearing shaft without a hinge (Fig. 2.5, c) is a design diagram of a “shaft-to-shaft” connection of the first type, a four-bearing shaft with a hinge
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
(Fig. 2.5, d) – design diagram of the “shaft to shaft” connection of the second type, three-bearing shaft (Fig. 2.5, e) – design diagram of the “shaft to shaft” connection of the third type.
Since the “shaft-to-shaft” connection forms a statically indeterminate design pattern of the shafts being connected, manufacturing and assembly errors can lead to significant forces in the supports. To limit the magnitude of these forces, it is necessary to take into account the relationship of reactions in the supports with errors in the location of the surfaces of parts, bending rigidity of shafts, contact stiffness of bearings, radial clearances in bearings, and assign location tolerances based on the statically indeterminate system under consideration.
In addition to an increase in reactions in the supports, which reduces the life of the bearings, in a “shaft-to-shaft” connection, fretting may occur in the mating of the contacting surfaces of the output end of the motor shaft and the hole in the gearbox shaft. To prevent the occurrence of fretting, the SEW company (Germany) recommends applying NOCO anti-seize paste to the contacting surfaces during assembly, Italian companies - Klűberpaste-46MR401 paste, company
Ivanov A.S., Murkin S.V. "Design of modern geared motors"
Gears. But a single part is not a machine. And in order to create a machine from parts, you must first of all know how to reliably connect them together with minimal technical equipment, and how to find the only acceptable connection option for each specific case.
Today we are talking about connecting rollers, gears, cams and other structural elements with shafts and moving axles, as well as shafts with each other. All connection methods that we will talk about are available to you if you have minimal equipment in a home workshop or garage: and machines. And these methods will be useful when building a wide variety of mechanisms and...
The key is a small but very important detail. It prevents one mating part from rotating relative to the other. The key is very simple to manufacture and assemble; it does not require additional dimensions; it will be hidden inside the assembly unit. In the part that is mounted on the shaft, and on the shaft itself, grooves are made, the dimensions of which are carefully adjusted to the keyed ones (Fig. 1).
The key can be considered an example of exceptionally rational use of material. There are no frills in it, all the material is in use: the side faces resist crushing deformation, which determines the length and height of the key, and its cross-section resists shear deformation, which gives the third dimension - thickness. The sizes of keys are standardized and, as a rule, are not calculated, but are selected from technical reference books, mainly depending on the diameter of the shaft.
The word "spline" comes from the German Spon- sliver. Apparently, it was the sliver that served as a key in the first mechanical parts created by human hands even before our era, for example, a windmill.
If the machine shaft operates under increased load and the key cannot withstand it, you can use a spline connection, which is like a family of keys made directly in the mating parts (Fig. 2). This fit of the part on the shaft is more reliable and stronger, but it is technologically much more complicated and, therefore, more expensive.
And here is another method for obtaining a strong and reliable connection of parts - a fit with a guaranteed interference fit. The shaft mounting diameter is made several hundredths of a millimeter larger than the diameter of the hole in the mating part. When a part is pressed into place, enormous frictional forces between the surfaces of the connected parts firmly fix their relative positions. It would seem that you couldn’t imagine anything simpler: no additional parts, no soldering, no welding, nothing superfluous, but... Imagine that we connected a shaft with a gear in this way, and it was necessary to remove it when repairing the mechanism. Of course, during disassembly, the seating surfaces of the parts will be damaged and it will not be easy to restore a reliable fit. Therefore, press fit is recommended only for machine components that cannot be disassembled.
Take a look at how a knife is installed manually on the auger shaft. This is an example of a common detachable connection of rotating parts - a square fit. But despite all its simplicity, reliability and compactness, this method is also not without sin, since it does not ensure the alignment of the mating parts (note that alignment is not required). However, if necessary, this drawback can be combated: additional cylindrical mounting surfaces A are provided on the shaft and hub of the installed part, the length of which must be no less than the mounting diameter (Fig. 3). This part of the landing takes care of centering. True, one of the positive qualities is already lost here - compactness
Instead of a square, you can provide a seating cone in the parts (K = 1:10) and get a more reliable connection, in which, moreover, when the nut is tightened tightly, backlash is eliminated. Sometimes, to fix the part on the shaft, a key is also inserted into the connection (Fig. 4), preferably a segment one, which, due to its configuration, is independently oriented in the inclined groove of the part being installed. By the way, sometimes a segment key is also used to fit parts onto a cylindrical shaft.
To transmit small torques, you can use simpler means of connecting parts to shafts and moving axes.
The part is installed on the roller and fixed in its designated place with a cylindrical pin (Fig. 5a). The through hole is drilled in such a way that the pin can be firmly driven into it with light blows of a hammer. During disassembly, the pin is also knocked out with a hammer using a bit or drift of the appropriate diameter.
A tighter and more reliable fastening of the part to the shaft can be achieved with a conical pin (Fig. 5b). To do this, the hole drilled for the pin is refined with a small conical reamer - a colisaurus.
However, even this simplest method of connecting parts cannot be used, as they say, without caution. You must first make sure that the part being installed will not block access to the drilling site, and not only to the drill, but also to the chuck in which it is clamped. The most common pin diameters are 1-3 millimeters, and such drills are very short. It is not recommended to do it under a pin.
If you make a threaded hole in the part to be installed and screw in a screw, its end, resting against the roller, will secure the part in a given place. This method gave rise to the term - set screw. Let's look at some of the types of set screws.
When screwed in, a pointed set screw seals the fit and, digging its tip into the body of the roller, holds the part (Fig. 6a).
A small groove is made along the axis of the roller into which the conical part of the set screw fits. The angle of the screw tip and groove is 90° (Fig. 6b). This method of fastening is somewhat stronger than the previous one: not only the tip, but almost the entire conical part of the set screw works here.
You can remove the flat where the part fits on the shaft, then you should use a set screw with a flat end (Fig. 6c).
Now briefly about the connections between the shafts. How, for example, does one connect an electric motor shaft to a gearbox shaft? The answer is simple - a clutch. But which one? The choice is wide: there are purely mechanical, hydraulic, electromagnetic, mixed type couplings - this is based on the principle of operation. And according to their design, they can be of constant and intermittent action, they can be frictional with a smooth clutch and gear with a fixed engagement, overrunning or single-acting, automatic and semi-automatic, with continuous remote control and with control according to a predetermined program. The great variety of clutch types is impossible to simply list.
For a first acquaintance, let's take a few simple ones.
Figure 7 shows a permanent coupling option. The ends of the connected rollers fit into a small sleeve with a gap and are secured with conical pins placed perpendicular to each other. Thanks to the gap, a cardan-type connection is obtained, which transmits rotation and compensates for the misalignment of the shafts resulting from inaccurate installation. Losses on and associated wear of rubbing parts are reduced. Installing such a coupling requires extreme care, especially on small rollers - if they are bent, the entire system may break.
Figure 8 shows a movable coupling. The ends of the shafts are made in the form of a tongue and groove, which, when articulated, allows some freedom of movement along the axis of rotation, but does not tolerate misalignment of the shafts.
To connect shafts with a diameter of 12 to 100 millimeters, elastic couplings with an asterisk are recommended (Fig. 9). At the ends of the shafts, steel coupling halves are attached, connected by an intermediate elastic sprocket made of hard rubber. The sprocket, having some elasticity, smoothes out beats from shaft misalignment and softens the blow at the moment of switching on. And another valuable quality is that this type of coupling operates almost silently.
Elastic coupling with an asterisk: 1 - coupling halves; 2 — asterisk; 3 — installation screws; 4 — retaining rings
To transmit small torques, modellers often use a simplified version of an elastic connection - a disk coupling. Here, the role of a sprocket is played by a rubber disk, and massive coupling halves are replaced by simple leads (Fig. 10).
To conclude the conversation, we will get acquainted with the principle of operation of a friction clutch using the example of a car clutch, which serves to disconnect the engine crankshaft from the car’s power transmission during gear shifting and braking. In addition, the clutch makes it possible to smoothly move the car from a standstill (Fig. 11).
Diagram of the car clutch mechanism: a - clutch engaged, b - disabled
The clutch disc 2 is pressed against the rotating flywheel 1 under the pressure of the spring 5, the hub 7 of which is seated on the splines of the drive shaft 6. When there is sufficient friction, the flywheel and clutch disc will rotate as one unit, transferring torque from the engine to the transmission.
If you press pedal 3, the drive force acting through tap 4 on hub 7 of the clutch disc will cause it to move along the splines of shaft 6. A gap will form between the flywheel and the clutch disc—the clutch will disengage. If you smoothly release the clutch pedal, spring 5 will press the clutch disc against the flywheel again, first with slipping (the car will move off smoothly), and then very tightly.
So, to connect rotating parts, human thought went from using elementary wood chips to creating the smartest automatic systems.
TO category:
Repair and construction machines
Shafts, axles, their supports and connections
Shafts and axles are supporting and rotating parts of machine elements. The axles only support the parts, and the shafts transmit torque. The parts of shafts and axles that transmit loads to the supports are called journals, and if they are located at the ends of the shafts, they are called tenons or trunnions. The supporting parts of vertical shafts and axes that transmit longitudinal loads are called heels.
Shafts can be smooth, stepped, cranked, cardan, flexible, etc. (Fig. 2.11). Smooth and stepped shafts are used in gearboxes, open and closed gears.
Crankshafts are used in crank mechanisms. Flexible and cardan shafts are used to transmit motion with frequent changes in the relative position of the connected units with a relatively large distance between them.
Rice. 2.11. Types of shafts: a - smooth; b - stepped; c - cranked; g - flexible
Rice. 2.12. Sliding bearings: a - one-piece with bushing; b - detachable with liners; 1 - bushing (liner); 2 - self-aligning support; 3 - body; 4 - hole for lubrication
Sliding bearings can withstand significant loads, are convenient for mounting large shafts when disassembling the bearings is required, are reliable when working in heavily polluted environments, and are relatively durable.
Rolling bearings (Fig. 2.13) consist of outer and inner rings with raceways and are made of alloyed wear-resistant chromium steel. Balls (for ball bearings) or rollers (for roller bearings) move between the rings along the raceways. The position of the rolling elements is fixed using separators - steel rings with holes for balls or rollers. Rolling bearings have 5...10 times less friction force compared to plain bearings. Roller bearings have a significantly higher load capacity than ball bearings, but the permissible rotation speed for them is approximately two times lower.
Rolling bearings are divided into six series depending on the load capacity (from ultra-light to extra-heavy) and into nine types according to their design.
Rice. 2.13. Rolling bearings: a - ball bearings with a separator; 6 - ball in the housing; c - ball thrust; g - double-row ball; d - roller; e - conical roller; g-roller self-aligning; z - multi-row roller
To reduce wear, rolling bearings are filled with grease and various seals (oil seals) made of felt, leather, etc. are used.
Couplings are used to connect shafts, as well as to transmit torque to parts and shafts of the kinematic chain of machines. According to their purpose, couplings are divided into connecting (elastic) and coupling. An example of the first type of couplings are sleeve (Fig. 2.14, a) and flange (Fig. 2.14, b). In sleeve couplings, the element connecting the shafts is a sleeve with a pin or pin. The connection of these couplings is made by longitudinal movement of shafts, gearboxes, drums, etc.
Connecting parts, pins and keys are subject to calculations. When using flange couplings, flanges are put on the ends of the shafts to be connected, which are then bolted together.
Rice. 2.14. Connecting couplings: a - bushing; b - flange
Couplings come in cam and friction types. Cam couplings (Fig. 2.15, a) consist of two coupling halves, one of which is permanently rigidly connected to the shaft, and the second can move along the shaft on a key or splines. At the ends of the coupling halves there are cams - protrusions and depressions, which, when the coupling halves approach each other, engage. Cam clutches can be used to stop or slow the mechanisms while rotating.
When making a working drawing of gears, there are various shapes of the mounting hole in the wheel hub. This depends on the type of connection between the wheel and the shaft.
9.4.1. Keyed connection
The main elements of this connection are shown in Fig. 9.7. In this case, the key fits approximately half its height into the groove (groove) of the shaft and half into the groove of the wheel hub. The lateral working faces of the key transmit rotation from the shaft to the wheel and back.
Rice. 9.6. Spur gear drawing
Table 9.2
Dimensions of keyed elements
|
Shaft diameter |
Key section dimensions |
Groove depth |
Shaft diameter |
Key section dimensions |
Groove depth |
|||||||||||||
|
t 1 |
t 1 |
|||||||||||||||||
Rice. 9.8. Elements of a keyed connection: a) keyway on the hub;
b) keyway on the shaft; c) keyed connection between the shaft and hub
9.4.2. Spline connection
The spline connection of the wheel hub with the shaft is carried out through several protrusions (splines), made integral with the shaft, and corresponding grooves cut into the hub (Fig. 9.9).
Spline joints of various profiles are produced: straight-sided, trapezoidal, involute and triangular. The straight-sided profile is the most common.
The rules for executing conventional images of splined shafts and wheel hubs on working drawings are established by GOST 2.409-74. An example image is shown in Fig. 9.10.
Rice. 9.10. Conventional images of splined shaft and hub elements
The symbol for the splines of a hole or shaft is indicated on the shelf of the leader line or in the technical requirements. Example of a symbol for a hub: 8 x 42 x 48, Where Z=8– number of teeth; d = 42- inner diameter; D=48- outside diameter. Tooth width b” is marked on the image.
4.2.1 Reading the assembly drawing. Reading an assembly drawing means determining the device, operating principle, purpose of the product depicted on it, imagining the interaction of parts, their shape and methods of connecting to each other. The sequence of reading the assembly drawing: − familiarization with the product. Using the main inscription, determine the name of the product, designation of the drawing, scale of the image, mass of the assembly unit; − image reading. Determine the main view, additional and local views, sections and sections, the purpose of each of them; − study of the components of the product. Determine from the specification the number and name of the parts included in the assembly unit, and from the drawing determine their shape, relative position and purpose. Find the image of the part first in the view on which the position number is indicated, and then in the others. It must be remembered that the same part on any section (section) is hatched in the same direction with the same step; − study of the functional purpose of the product and its design solution. Establish a method for connecting individual parts to each other, the interaction of components during operation, external interconnection with other assembly units and products. For detachable connections, identify all fasteners. Determine the mating surfaces and dimensions along which the parts are mated; − study of product design. Establish the nature of the connection of parts, their functional interaction during operation, connection and interaction with other assembly units. For moving parts, establish the process of their movement during operation of the mechanism, determine the rubbing surfaces and methods of lubrication; − determining the order of assembly and disassembly of the product is the final stage of reading the drawing.
Sequence and basic techniques for reading drawings
Read assembly drawing - this means presenting the shape and design of the product, understanding its purpose, operating principle, assembly order, and also identifying the shape of each part in a given assembly unit. When reading a general view drawing you should: 1. Find out the purpose and operating principle of the product. The necessary information about the purpose and operating principle of the product is contained in the main title and description of the product. 2. Determine the composition of the product. The main document for determining the composition of a product is the specification, in which the component parts of the product are classified into sections. To determine the position of a specific component of a product in the drawing, you need to determine the position number in the specification by its name, and then find the corresponding leader line in the drawing. The specification also allows you to determine the number of products of each item. 3. Determine the purpose and configuration of the component parts of the product. The purpose and configuration of the product is determined by the functional features of the product as a whole and its components. The configuration of the components is determined by their purpose and interaction during operation. When determining the configuration of components, attention should be paid to the way they are connected. 4. Identify ways to connect the component parts of the product to each other. The methods of connecting parts are determined by the peculiarities of the interaction of the elements of the product during its operation. Connection methods can be identified from a general drawing and classified as detachable or permanent. 5. Determine the sequence of assembly and disassembly of the product. One of the main requirements for the design of a product is the ability to assemble and disassemble it during operation and repair. Only a design that allows assembly (disassembly) using a minimum number of operations can be considered rational. The following sequence of reading the drawing is recommended: 1. Based on the main inscription, determine the name of the product, number, scale of the drawing, weight of the product, and the organization that issued the drawing. 2. Find out the contents and features of the drawing (identify all the images that make up the drawing). 3. According to the specification, establish the name of each part of the product, find its image in all images, and understand its geometric shapes. Since drawings, as a rule, contain not one, but several images, the shape of each part can be identified unambiguously by reading all the images in which this part appears. You should start with the simplest parts in shape (rods, rings, bushings, etc.). Having found a part in one (usually the main) image using a positional designation and, knowing the structural purpose of the part, imagine its geometric shape. If this one image unambiguously determines the shape and dimensions of the part, then proceed one by one to identifying the shapes of other parts; if one image does not reveal the shape or dimensions of at least one element of the part, then you should find this part in other images of the assembly drawing and make up for the insufficiency of one image. Clarification of the shape of a part is facilitated by the fact that in all sections and sections the same part is shaded with the same slope and distance between the hatching lines. At the same time, they use knowledge of the basics of projection drawing (projection connection of points, lines and surfaces) and conventions established by ESKD standards. 4. Read the product description. If there is no description, you should, if possible, read the description of a similar design. 5. Establish the nature of the connection between the component parts of the product. For permanent connections, identify each element of the connection. For detachable connections, identify all fasteners included in the connection. For moving parts, establish the possibility of their movement during operation of the mechanism. 6. Determine which parts are lubricated and how lubrication is carried out. 7. Find out the procedure for assembling and disassembling the product. It should be borne in mind that in the specification and on the assembly drawing, the order of recording and designation of components is not related to the assembly sequence. It is recommended to record the procedure for assembling and disassembling the product on paper in the form of a diagram or in the form of recording the sequence of operations. The ultimate goal of reading a drawing, as a rule, is to clarify the structure of the product, the principle of operation and to establish its purpose. In the educational process, the central place in reading a drawing is occupied by the study of the shapes of individual parts, as the main means of clarifying all other issues related to reading a drawing.
Detailing the drawing
Detailing is the execution of working drawings of a part based on a general view drawing. Detailing – this is not a simple copying of an image of parts, but a complex creative work, including an individual assessment of the complexity of the shapes of each part and making the best graphic solution for it: choosing the main image, the number and content of images. The dimensions of the parts are measured in the drawing taking into account the scale indicated in the main inscription. The exception is the dimensions shown on the assembly drawing. The dimensions of standard elements (threads, tapers, turnkey, etc.) are specified according to the relevant standards. Detailing process It is advisable to divide it into three stages: reading the general drawing, detailed identification of the geometric shapes of the parts and execution of working drawings of the parts. 1. Reading a general view drawing. The result of reading a general view drawing should be an understanding of the composition of the parts included in the assembly, their relative position and methods of connection, interaction, structural purpose of each part separately and the product as a whole. 2. Detailed identification of geometric shapes of parts to be drawn, in order to correctly select the main image, the number and content of other images on the working drawings. As the shapes of the parts are identified, the issue of choosing the main image and the need to make other images for each part should be decided, and the image scale and format should be selected. 3. Execution of working drawings of parts. layout the drawing, i.e. outline the placement of all images of the part in the selected format. Draw the necessary views, sections, sections and extension elements in thin lines. draw extension and dimension lines. Determine the true dimensions of the part elements and mark them on the drawing. Pay special attention to ensure that there are no discrepancies in the dimensions of the mating parts. Determine the necessary structural and technological elements (chamfers, grooves, slopes, etc.), which are not shown on the general drawings. The dimensions of the identified structural elements are determined not according to the general view drawing, but according to the relevant standards for these elements. indicate the roughness based on the manufacturing technology of the part or its purpose. outline the drawing and shade the cuts and sections. check the drawing and make corrections if necessary. fill out the title block and write down the technical requirements.
