Reduction gears, worm

Mixing by means of a draw-lift turbine is the most modem and efficient method (Fig. 33). The turbine is rotated at high speed (several hundred r.p.m.) and powered by an electric motor with a worm reduction gear. The turbine draws the liquid... 

Either splash lubrication or forced-feed oil lubrication is commonly used for rotating machinery such as turbines, pumps, compressors, reduction gears, and worm gears. Splash lubrication is used for relatively slow-speed machinery, while high-speed machinery always requires forced-feed lubrication. 

Top entering mixers are heavy duty equipment. They are usually fixed to a rigid structure or tank mounting. Either radial flow or axial flow turbines may be used. Speeds vary from 50 to 100 rpm and usually require a double set of helical gearing or a single set of worm gears to achieve these low speeds. Therefore, they are more expensive than single reduction mixers. 

The worm thread is a major factor in worm ratios and is an important feature in worm design. The speed-reduction ratio is equal to the total number of worm-gear teeth divided by the number of worm threads. 

Oil dip-lubricated, single-reduction worm gear, 1500 rpm input 78 11 5 6... 

The high-speed drive motor is coupled to the low-speed screw with a reducer or gearbox. Typical reduction rations are 15 1 or 20 1. Although helical gears are most common, worm gears are used on older or very small machines. 

Other types of motors that may be encountered in mixer applications are gear motors, pony motors, and brake motors. Gear motors are composed of an electric motor with an attached gear reducer. Spur, helical, or worm gears can be used in single or multiple reductions to achieve a wide range of output speeds. Motor power, output speed, and output torque are all essential design variables. 

Actuation of the control rod is performed by the drive uiit (Fig, 95). The unit consists of a housing that contains the worm and worm wheel drive and the drive pinion and rack. The lower end of the rack is secured to the upper carriage top plate. Lubrication for the bearings and gear is contained within the housing by a series of oil seals. Power is supplied to the worm drive by an electric motor and reduction init. 

The crown of this reduction could not be used to transfer motion to the rack because of its shape coupled with the worm, so in the same axis it was placed a helical gear teeth to transmit the movement to the rack, so the gear box is divided into two parts, facilitating the scaling ... 

Special reducers. Special reducers in various combinations are also available. An example is presented in Fig. P-29, which shows a large vertical-output-shaft imit with a single worm reduction having 38-in gear centers, which is used in pulverized-coal service. 

Number of threads in worm. The minimum number of teeth in the gear and the reduction ratio will determine the number of threads for the worm. Generally 1 to 10 threads are used. 

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