Type of gears - Screw Gears (Crossed Helical Gears)

Video

Screw gears, or crossed helical gears, transmit power between two non-intersecting, non-parallel shafts, typically at a 90-degree angle. They are a type of helical gear but differ from parallel helical gears in their shaft orientation and point contact, which means they handle lower loads and have lower efficiency. They are suited for light-duty applications, and often one gear is made of a softer material like bronze to prevent excessive wear due to the high sliding friction between the teeth.

Key features and advantages:

Smooth and quiet operation: The helical teeth engage gradually, leading to smoother and quieter performance compared to spur gears. Reduced vibration: The continuous contact of the teeth helps to reduce vibration and shock loads, which can extend the service life of the gears. High load capacity: The angled teeth distribute the load over multiple teeth, increasing their load-carrying capacity.

Disadvantages

Low efficiency: The sliding contact between the teeth causes significant friction, which leads to power loss and reduced efficiency. High wear: The point-to-point, sliding contact causes a high rate of wear on the teeth over time. High lateral forces: The helical tooth design generates strong lateral (sideways) forces that must be absorbed by the bearings. Requires special lubrication: Due to high friction and wear, these gears require specialized lubrication, like special hypoid gear oils, to function properly. Limited load capacity: The point contact limits the amount of force the gears can handle, making them unsuitable for high-torque or high-speed applications. Requires special bearings: The lateral forces generated by the gears necessitate the use of special thrust bearings to manage the loads on the shafts.

How they work

Screw gears, or crossed helical gears, work by transmitting motion between non-intersecting shafts through a sliding, screw-like motion rather than a rolling motion. Unlike parallel helical gears, screw gears have different helix angles but the same hand (both left or both right). The meshing of their teeth generates point contact, which results in constant sliding between the gear faces and necessitates special lubrication to prevent excessive wear.

Materials and applications

Materials: They are made from various materials, including plastic (like acetal or nylon) and metals (like aluminum, brass, and stainless steel) Applications: They are widely used in industries such as automotive, manufacturing, and consumer electronics. Plastic gears: These are lightweight, non-rusting, and can operate without lubrication, making them suitable for food production and medical equipment. Metal gears: These offer greater strength, load-carrying capacity, and heat resistance.