Internal Gears For Power Transmission
An internal gear is a gear, cut into the cylinder surface that then meshes with a spur gear. These days gear cutting is now best produced using a skiving machine.
Hobbing machines are used to produce internal gears. Cutting internal gears, cutting splines, and cutting sprockets on a hobbing machine use teeth or splines that are progressively cut into bar stock or a steel cylinder. A series of cuts are made by the hob. It is relatively inexpensive and accurate and can produce large quantities of parts.
Hobbing internal gears, is the most widely used gear cutting process for creating spur and helical gears. Skiving is similar to hobbing external gears and it can be applied to the cutting of internal gears. Internal gears are skived with a rotary cutter.
Internal gears can be used with the same module spur gears, depending on the number of teeth combinations, but it is necessary to note the possibilities of getting involute, trochoid or trimming interference.
Internal gears are often used in applications involving planetary gear drives and gear couplings. There are three major types of planetary gear mechanisms: planetary, solar and star types. Depending on the type and the pattern of which shafts act as input and output, many variations of speed transmission ratios and rotational directions are produced.