ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm equipment because of increased driving efficiency ( 6-10% higher on 25:1 ratio) and increased loading capacity (on the subject of 30%).
The disadvantage of a globoid gear is higher manufacturing cost and sensitivity of the enveloping pinion to the axial location.
Due to the geometrical nature of the tooth geometry Globoid pinion may mesh not merely with the mating enveloping gear but also with a properly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is certainly common in reduced cost in applications such as for example automotive electric powered gear actuators. The significant price advantage comes due to the probability to injection mold the 
helical plastic gear. The load capability of the simplified helical/Globoid transmission is decreased to the level below the strain capacity of the standard worm gear. Nevertheless the driving efficiency continues to be better compare to the regular worm gear.
There are only a few suppliers of the Globoid gear. division of Textron, positioned in Traverse Town, MI. The detailed information about processes utilized at Cone Drive for making of its gear could not be found. However, predicated on publicly released details it can be understood that the apparatus is manufactured by CNC milling with use a small ball shaped cutter.
Ever-power has capability to design, prototype and supply Globoid gear products. The expertise of Ever-power is 3-dimentional simulation and modeling of the Globoid and double enveloping tooth geometry. Ever-power 3-dimentional Globoid and double enveloping equipment CAD models can be used in numerous CNC machining shops for creating globoid gear at significantly reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that manufacturing of the Globoid equipment is more complex compare to production of the Globoid pinion. The Globoid pinion could be produced in high amounts by turning, whirling or grinding. During the machining procedure for the Globoid pinion the slicing tool has to be able to tilt to be able to produce the enveloping shape.
The newer production methods are under development. The most promising production method of the Globoid pinion is certainly continues grinding procedure, which incorporates a grinding steering wheel (diamond or CBN plated) with particular Ever-power simulated geometry. The complication of the novel process is the difficulties with simulation of the geometry of the grinding device. The grinding tooth would have to generate a correct type of the Globoid pinion without tilting so the production price and the production price would be significantly reduced. Ever-power is rolling out a computer based device for producing of 3-dimensional CAD types of grinding tools for high volume creation of the Globoid items.
The most common usage of the Globoid gear set was seen in 1961-1989 on automotive steering systems in Italy and in Soviet Union.
VAZ-2101 with Globoid steering technology.
The Globoid pinions have been made by grinding with a tilting grinding wheel. The Globoid gears have been cut by a particular hub, which replicated the shape of the Globoid Pinion. Special machines for making the reducing hubs have been developed. Because the modern automotive steering systems began to use traditional Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears provides been reduced.
Variable ratio technology comparison
Bishop
Ever-power
Vr-rack technology was introduced:
Before 2000
2000
Underlying mathematical model is founded on:
Classic
gear
theory
Direct
Digital
Simulation
Rack geometry calculation precision is:
Limited by the boundaries of the traditional gear theory
Unlimited
Capability to produce the vr-rack with not involute type for reduced noise
NO
YES
Capability to generate vr-rack with an increase of ratio gain is:
Limited
YES
Cost of vr-rack style is:
High
Low
Ever-power advanced Adjustable Ratio rack and pinion high ratio gain technology for engine sport racing applications.
Ever-power low noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another generation of Globoid gears. In 1999 Ever-power presented a skew axis Globoid gear as a higher load capability and increased driving efficiency option to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It needs to be noted that the name WORMOID does not relate with any scientific term in fact it is something of Dr. Stepan V. Lunin, who was the initial in proposing this design and, more importantly, he was the initial who produces an accurate functioning model of the gear in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID equipment has proved the capability of the idea such as for example conjugated transmission actions and significant boost of number of tooth in the contact compare to the traditional Globoid gear.
CAD 3-d model of Ever-power wormoid gear.
Ever-power is currently offering assistance for design and development of items predicated on Ever-power wormoid technology.
It needs to be noted that wormoid gear design from Ever-power is obviously promising unique advantages review to the basic Globoid (double enveloping) gear. One of the obvious advantages is elevated load capacity due to increased number of one’s teeth in the mesh. The gear torque is usually carried by even more teeth so the load on each individual tooth is reduced. The other obvious advantage is boost driving efficiency. As you can see, the part of the pinion with larger diameter is traveling the corresponding part of the gear, that includes a larger diameter as well. Such of unique feature of Ever-power wormoid is normally missing in the classic Globoid gear and outcomes in higher sliding velocities and higher friction medication on the classic globoid gear. A skilled in the artwork engineer would immediately derive possible design benefits of the wormoid equipment. For example, using of the wormoid gear can significantly reduce price of electric powered globoid worm assist mechanisms that are generally applied to modern automobiles. Because of the bigger driving efficiency, wormoid equipment set can be designed with increase ration and offer the same driving efficiency as the initial worm or dual enveloping worm gear. For instance NSK worm gear steering actuator with a ration around 20:1 delivers about 80% of driving efficiency. The plastic equipment would hold about 80 Hm of torque. An alternative wormoid gear style from Ever-power would be capable to boost the ratio up to 30:1 and the torque on the apparatus up to 150 Hm without enhance of the center distance between the equipment and the pinion.
