Herringbone Gear

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herringbone gear

[′her·iŋ‚bōn ‚gir]
(mechanical engineering)
The equivalent of two helical gears of opposite hand placed side by side.

Herringbone Gear

 

a spur gear with V-shaped helical teeth. The mutual inclination of the tooth segments on opposite sides compensates the axial thrust produced by single helical gears. Herringbone gears afford smooth operation and increased load-carrying capacity, which are characteristic of helical gear transmissions in general. They are used in medium-size and large transmissions, including special transmissions operating at pitch-circle velocities up to 200 m/sec (turbine reduction gears).

Figure 1. Herringbone gears: (a) continuous-tooth type, (b) double helical gears, (c) two pairs of gears

Continuous-tooth herringbone gears (Figure 1,a) require special equipment to machine the teeth. Double helical, or conventional herringbone, gears (Figure l,b) have a gap, or groove, where the two sets of teeth meet; they may be made on ordinary gear-hobbing machines, but the width of the gear wheel must be increased by the width of the groove g. Transmission through two pairs of helical gears with opposed teeth (Figure 1,c) enables the space between the gears to be used for another transmission.

References in periodicals archive ?
The steam turbine rotor is connected by a coupling 12 to the ordinary double-helical gear train with the speed ratio 1:5.3448 (pinion [z.sub.1] = 29, gear [z.sub.2] = 155) and the second unit gear transmission speed ratio is 1:6.857 (pinion [z.sub.1] = 21, gear [z.sub.2] = 144) that reduces turbine rotor high rotational speed to 1500 rpm of the generator rotor 11.
At the heart of the gear pump is a pair of double-helical gear rotors, supported by roller bearings.
In other cases, a swivel-head cutter is employed for the machining of double-helical gears with gap widths as narrow as 1/2 inch.