globoid worm

ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm gear due to increased driving efficiency ( 6-10% higher in 25:1 ratio) and increased loading capacity (about 30%).
The disadvantage of a globoid gear is higher production cost and sensitivity of the enveloping pinion to the axial location.
Because of the geometrical nature of the tooth geometry Globoid pinion may mesh not merely with the mating enveloping equipment but also with a properly designed cylindrical helical equipment. Using a helical equipment with a Globoid pinion is usually common in reduced cost in applications such as automotive electric powered gear actuators. The significant cost advantage comes due to the probability to injection mold the helical plastic material gear. The load capability of the simplified helical/Globoid transmitting is reduced to the level below the load capacity of the standard worm gear. Nevertheless the driving efficiency continues to be better evaluate to the standard worm gear.
There are only a few suppliers of the Globoid gear. division of Textron, positioned in Traverse Town, MI. The detailed details about procedures used at Cone Drive for manufacturing of its gear cannot be found. However, predicated on publicly released information it could be understood that the gear is produced by CNC milling with use a little ball shaped cutter.
Ever-power has capability to design, prototype and offer Globoid gear items. The experience of Ever-power is 3-dimentional simulation and modeling of the Globoid and dual enveloping tooth geometry. Ever-power 3-dimentional Globoid and double enveloping equipment CAD models can be used in various CNC machining shops for making 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 technical compare to production of the Globoid pinion. The Globoid pinion can be produced in high quantities by turning, whirling or grinding. Through the machining procedure for the Globoid pinion the cutting 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 approach to the Globoid pinion is certainly continues grinding procedure, which includes a grinding steering wheel (gemstone or CBN plated) with particular Ever-power simulated geometry. The complication of the novel procedure is the difficulties with simulation of the geometry of the grinding device. The grinding tooth would need to generate a correct kind of the Globoid pinion without tilting therefore the production price and the production price would be significantly reduced. Ever-power is rolling out a computer based tool for producing of 3-dimensional CAD types of grinding equipment for high volume production 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 already been cut by a particular hub, which replicated the form of the Globoid Pinion. Special machines for producing the trimming hubs have been developed. Because the modern automotive steering systems started to use classic Bishop or advanced Ever-power adjustable ratio rack and pinion technology, the demand for the Globoid gears has 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:
Tied to the boundaries of the classic gear theory
Unlimited
Capacity to produce the vr-rack with not involute form for reduced noise
NO
YES
Capability to generate vr-rack with increased ratio gain is:
Limited
YES
Cost of vr-rack design is:
High
Low
Ever-power advanced Variable Ratio rack and pinion high ratio gain technology for engine sport racing applications.
Ever-power low sound Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of another generation of Globoid gears. In 1999 Ever-power launched a skew axis Globoid gear as a higher load capability and increased driving globoid worm effectiveness alternative to the classic Globoid gear.
Ever-power skew axis (wormoid) gear.
It has 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 first in proposing this design and, more importantly, he was the first who produces a precise functioning 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 action and significant increase of number of tooth in the contact compare to the traditional Globoid gear.
CAD 3-d style of Ever-power wormoid gear.
Ever-power is currently offering assistance for design and development of items based on Ever-power wormoid technology.
It has to be noted that wormoid equipment design from Ever-power is obviously promising unique advantages compare to the classic Globoid (double enveloping) equipment. Among the obvious advantages is increased load capacity because of increased number of one’s teeth in the mesh. The gear torque is certainly carried by more teeth therefore the load on every individual tooth is reduced. The other obvious advantage is increase driving efficiency. As you can see, the portion of the pinion with larger diameter is generating the corresponding portion of the gear, that includes a larger diameter aswell. Such of exclusive feature of Ever-power wormoid is normally missing in the traditional Globoid gear and results in higher sliding velocities and higher friction medication on the traditional globoid gear. A skilled in the art engineer would instantly derive possible design advantages of the wormoid equipment. For example, using of the wormoid equipment can significantly reduce price of electric powered support mechanisms that are generally used on modern automobiles. Because of the higher driving efficiency, wormoid gear set can be designed with increase ration and provide the same driving efficiency as the original worm or dual enveloping worm equipment. For instance NSK worm gear steering actuator with a ration of about 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 will be capable to increase the ratio up to 30:1 and the torque on the gear up to 150 Hm without enhance of the center distance between the gear and the pinion.

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