GEAR TYPES &
`MANUFACTURING
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`sdp-si.com/resources
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`1. Spur Gear
`This is a cylindrical shaped gear in which the teeth are
`parallel to the axis. It has the largest applications and,
`also, it is the easiest to manufacture.
`
`2. Helical Gear
`This is a cylindrical shaped gear with helicoid teeth. Helical
`gears can bear more load than spur gears, and work more
`quietly. They are widely used in industry. A disadvantage is the
`axial thrust force the helix form causes.
`
`3. Double Helical Gear
`This is a gear with both left-hand and right-hand helical teeth.
`The double helical form balances the inherent thrust forces.
`
`4. Screw Gear (Crossed Helical Gear)
`Two helical gears of opposite helix angle will mesh if their
`axes are crossed. As separate gear components, they are
`merely conventional helical gears. Installation on crossed
`axes converts them to screw gears. They offer a simple
`means of gearing skew axes at any angle. Because they have
`point contact, their load carrying capacity is very limited.
`
`5. Internal Gear
`This is a cylindrical shaped gear but with the teeth
`inside the circular ring. It can mesh with a spur gear.
`Internal gears are often used in planetary gear systems.
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`6. Spur Rack
`This is a linear shaped gear which can mesh with a
`spur gear with any number of teeth. The spur rack is a
`portion of a spur gear with an infinite radius.
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`7. Helical Rack
`This is a linear shaped gear which meshes with a helical gear.
`Again, it can be regarded as a portion of a helical gear with
`infinite radius.
`
`8. Face Gear
`This is a pseudobevel gear that is limited to 90O intersecting axes.
`The face gear is a circular disc with a ring of teeth cut in its side
`face; hence the name face gear. Tooth elements are tapered
`towards its center. The mate is an ordinary spur gear. It offers no
`advantages over the standard bevel gear, except that it can be
`fabricated on an ordinary shaper gear generating machine.
`
`9. Straight Bevel Gear
`This is a gear in which the teeth have tapered conical
`elements that have the same direction as the pitch cone
`base line (generatrix). The straight bevel gear is both the
`simplest to produce and the most widely applied in the
`bevel gear family.
`
`10. Spiral Bevel Gear
`This is a bevel gear with a helical angle of spiral teeth.
`It is much more complex to manufacture, but offers a
`higher strength and lower noise.
`
`13. Zerol Gear
`Zerol gear is a special case of spiral bevel gear. It is a spiral
`bevel with zero degree of spiral angle tooth advance. It has
`the characteristics of both the straight and spiral bevel gears.
`The forces acting upon the tooth are the same as for a straight
`bevel gear.
`
`14. Hypoid Gear
`This is a deviation from a bevel gear that originated as
`a special development for the automobile industry. This
`permitted the drive to the rear axle to be nonintersecting,
`and thus allowed the auto body to be lowered. It looks
`very much like the spiral bevel gear. However, it is
`complicated to design and is the most difficult to produce
`on a bevel gear generator.
`
`11. Worm And Worm Gear
`Worm set is the name for a meshed worm and worm gear. The
`worm resembles a screw thread; and the mating worm gear
`a helical gear, except that it is made to envelope the worm as
`seen along the worm’s axis. The outstanding feature is that the
`worm offers a very large gear ratio in a single mesh. However,
`transmission efficiency is very poor due to a great amount of
`sliding as the worm tooth engages with its mating worm gear
`tooth and forces rotation by pushing and sliding. With proper
`choices of materials and lubrication, wear can be contained
`and noise is reduced.
`
`12. Double Enveloping Worm Gear
`This worm set uses a special worm shape in that it par-
`tially envelops the worm gear as viewed in the direction of
`the worm gear axis. Its big advantage over the standard
`worm is much higher load capacity. However, the worm
`gear is very complicated to design and produce, and
`sources for manufacture are few.
`
`FUJIFILM, Exh. 2003, p. 1
`FUJIFILM v. Sony, 2018-00876
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