Helical toothing

This led to the knowledge that extreme high-speed gears, which must be equipped with toothed couplings for lateral critical speed reasons, should have a single helical toothing that is not affected by additional external thrusts. 

On a double helical toothing, an external thrust would act on one helix only, which is considered a worst-case situation for the toothing. 

A double-helical design should be considered, particularly for critical service. Rotation of the helices should be such that they will be apex leading, that is, teeth engage at the centers with mesh progressing to the tooth outer ends. Additionally, rotation should permit the force from the gear mesh to cause the gear to load the lower half of its bearings. The... 

The use of spur gears in gear pumps will produce in the discharge pulsations having a frequency equiv ent to the number of teeth on both gears multiplied by the speed of rotation. The amplitude of these disturbances is a function of tooth design. The pulsations can be reduced markedly by the use of rotors with helical teeth. This in turn introduces end thrust, which can be eliminated by the use of doublehelical or herringbone teeth. 

Gear Pumps When two or more impellers are used in a rotary-pump casing, the impellers will take the form of toothed-gear wheels as in Fig. 10-54, of helical gears, or of lobed cams. In each case, these impellers rotate with extremely small clearance between them and between the surfaces of the impellers and the casing. In Fig. 10-54, the two toothed impellers rotate as indicated by the arrows the suction connection is at the bottom. The pumped liquid flows into the... 

This cutter has teeth on the periphery only, and is used to produce flat surfaces parallel to the axis of the cutter. Fig. 11.8(a). The teeth are helical, enabling each tooth to take a cut gradually, reducing shock and minimising chatter. Cylindrical cutters are made in a variety of diameters and lengths up to 160 mm diameter x 160 mm long. 

BAYDAR, N., CHEN, Q., BALL, A., KRUGER, U. (2001). Detection of incipient tooth defect in helical gears using multivariate statistics. Mechanical Systems and Signal Processing, 15 (5), pp. 303—321. 

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