SHAFT CONNECTIONS WITH CONNECTED ITEMS
When designing drives consisting of gears and worm wheels, sprockets of chain drives, pulleys of belt drives, spacers, bearings, it is necessary to ensure their precise installation on shafts, transmission of torque from the track, pulleys and sprockets to the shaft or in the opposite direction , provide for axial fixation of the specified parts on the shafts and the possibility of adjusting the axial position of the toothed or worm tracks, the clearances in the bearings.
"hub-hub" type connections
Various rigid connections are widely used to transfer the rotation from the shaft to the hub of the gear, pulley, sprocket and other coaxial parts, the main types of which are:
The elements of hard connections work on slice, bend and collapse.
The pins are cylindrical (Figure 4.1, a) or conical (Fig. 4.1, b) rods designed to fix the relative position of the fastened parts, as fasteners, to transfer small transverse forces and moments (mainly in instrument making). The pins are also used as a breakable part in the power transmission circuit, which protects the product from overloads.
The conical pins are made with a taper of 1:50, which ensures self-locking and centering of the parts.
Smooth pins - both cylindrical and conical - accurately fix the parts to be connected relative to each other, but require high precision in manufacturing and processing the holes.
Smooth pins in the holes are held by rubbing. To do this, the cylindrical pins are installed in the holes with interference, and when uneven loads are applied and at significant angular velocities, the cylindrical pins are additionally fixed in the holes by coring, flaring, riveting the ends (Fig. 4.2a) or by spring rings (Fig. 4.2b).
There is no need to unfold a hole under the studs that are pinned - the notches provide a reliable connection, but such pins provide less fixation accuracy.
The types, size intervals and materials of standardized pins are shown in Table. A.142.
22.214.171.124. Landing of the pin connection
The locating pins are usually installed in a fit fit in one of the parts to be joined. With the other part it is set to plant H1 (L6 or H7/H6.
Key connections are used to transfer torque. They are used at low loads, when the joints can be fixed or movable along the shaft axis, strained (with wedge and tangential keys) or unhardened (with prismatic and segmented keys).
Prismatic keys (Figure 4.3)
(Table A.143) produce the following three types:
• ordinary (GOST 23360-78) and high (GOST 10748-79), which are used for fixed joints of hubs with shafts;
• Shaft guides
(GOST 8790-79), used when the hubs must be able to move along the shafts;
• sliding assemblies (GOST 12208-66), connected to the hub with a projection (finger) of cylindrical shape and moving along the shaft together with the hub.
Wedge keys are a self-locking wedge with a slope of 1: 100; they are performed in accordance with GOST 24068-80. Wedge cords are divided into mortgages and paddles.
Paddles are made with heads for driving and retrieving dowels from the grooves.
Tangential keys differ from wedges in that the tension between the shaft and the hub will be created by them not in the radial, but in the tangential (tangential) direction. These keys are used mainly for heavily loaded shafts in the transmission of reversible movements; they are performed in accordance with GOST 24069-80 (normal) and GOST 24070-80 (reinforced).
Segmented keys (GOST 24071-80) (Figure 4.4) (Table A.144) are used on shafts of small diameters (up to 38 mm) and with a short hub; the connections are easy to manufacture and assemble, but the shaft is loosened by a deep groove under the key.
Round cylindrical and round conical keys (Figure 4.5) are not standardized. They are used in those cases if the bushing is to be installed on the shaft end. With a shaft diameter c1, the diameter of the round key (AND x is:
the length of the round key is:
The holes for these keys are obtained when assembled with collateral
landing with interference
The center of the hole should be shifted toward the center of the va
la (axis) over the distance:
the most common prismatic keys, which, but in comparison with whale, provide more convenient assembly and disassembly of parts, as well as their better centering.
If two prismatic keys are used, they are installed at an angle of 180 °.
The structure of the symbol for the keyed connection should look like this:
where 1 - the main landing dimension b (width of the key), mm; 2 - the field of access of the keyway; 3 - the key's tolerance field.
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