globoid worm

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 about 25:1 ratio) and increased loading capacity (about 30%).
The disadvantage of a globoid gear is higher manufacturing cost and sensitivity of the enveloping pinion to the axial location.
Because of the geometrical character of the tooth geometry Globoid pinion can mesh not merely with the mating enveloping equipment but also with a correctly designed cylindrical helical equipment. Using a helical gear with a Globoid pinion is certainly common in reduced cost in applications such as automotive electric powered gear actuators. The significant cost advantage comes because of the possibility to injection mold the helical plastic gear. The load capability of the simplified helical/Globoid transmission is decreased to the particular level below the strain capacity of the standard worm gear. However the driving efficiency is still better evaluate to the standard worm gear.
There are simply a few suppliers of the Globoid gear. division of Textron, located in Traverse Town, MI. The detailed details about procedures used at Cone Drive for developing of its gear cannot be found. However, based on publicly released details it can be understood that the gear 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 knowledge 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 generating globoid gear at significantly reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It needs to be noted that manufacturing of the Globoid equipment is more technical compare to manufacturing of the Globoid pinion. The Globoid pinion can be produced in high amounts by turning, whirling or grinding. During the machining process of the Globoid pinion the slicing tool needs to be capable to tilt in order to produce the enveloping shape.
The newer production methods are under advancement. The most promising production approach to the Globoid pinion is continues grinding process, which globoid worm incorporates a grinding wheel (diamond or CBN plated) with specific Ever-power simulated geometry. The complication of the novel procedure is the difficulties with simulation of the geometry of the grinding tool. The grinding tooth would have to generate a correct type of the Globoid pinion without tilting therefore the production price and the production cost would be considerably reduced. Ever-power has developed a computer based device for producing of 3-dimensional CAD models of grinding tools for high volume creation of the Globoid items.
The most common use of the Globoid gear set was noticed 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 special hub, which replicated the form of the Globoid Pinion. Special machines for producing the cutting hubs have already been developed. Because the modern motor vehicle steering systems began to use traditional Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears offers been reduced.
Variable ratio technology comparison
Bishop
Ever-power
Vr-rack technology was introduced:
Before 2000
2000
Underlying mathematical model is based on:
Classic
gear
theory
Direct
Digital
Simulation
Rack geometry calculation accuracy is:
Limited by the boundaries of the classic gear theory
Unlimited
Capability to produce the vr-rack with not involute type for reduced noise
NO
YES
Capacity to generate vr-rack with an increase of ratio gain is:
Limited
YES
Cost of vr-rack style is:
High
Low
Ever-power advanced Variable Ratio rack and pinion high ratio gain technology for motor sport racing applications.
Ever-power low noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another era of Globoid gears. In 1999 Ever-power released a skew axis Globoid gear as a higher load capability and increased driving effectiveness option to the classic Globoid gear.
Ever-power skew axis (wormoid) gear.
It has to be noted that the name WORMOID will not relate to any scientific term and it is something of Dr. Stepan V. Lunin, who was the first in proposing this style and, more importantly, he was the initial who produces an accurate operating model of the apparatus in 3-dimantional CAD system. The accurate 3-d CAD of the WORMOID gear has proved the ability of the idea such as for example conjugated transmission actions and significant increase of number of tooth in the contact compare to the classic Globoid gear.
CAD 3-d style of Ever-power wormoid gear.
Ever-power is currently offering assistance for style and development of items based on Ever-power wormoid technology.
It needs to be noted that wormoid gear style from Ever-power is actually promising unique advantages compare to the classic Globoid (double enveloping) equipment. One of the obvious advantages is increased load capacity due to increased number of the teeth in the mesh. The apparatus torque is normally carried by even more teeth therefore the load on each individual tooth is decreased. The other apparent advantage is boost driving efficiency. As one can see, the part of the pinion with bigger diameter is generating the corresponding part of the gear, which has a larger diameter aswell. Such of unique feature of Ever-power wormoid can be missing in the classic Globoid gear and results in higher sliding velocities and higher friction medication on the traditional globoid gear. An experienced in the artwork engineer would instantly derive possible design advantages of the wormoid gear. For instance, using of the wormoid gear can significantly reduce price of electric powered help mechanisms that are commonly used on modern automobiles. Because of the higher driving efficiency, wormoid gear set can be made with increase ration and provide the same driving performance as the original 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 gear would hold about 80 Hm of torque. An alternative wormoid gear design from Ever-power will be capable to raise the ratio up to 30:1 and the torque on the gear up to 150 Hm without increase of the center distance between the gear and the pinion.

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