globoid worm

ypical Globoid gear.
Globoid (or Double Enveloping Worm or Hour Glass) gear has advantage versus a traditional worm equipment due to increased globoid worm driving efficiency ( 6-10% higher about 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 character of the tooth geometry Globoid pinion can mesh not merely with the mating enveloping gear but also with a correctly designed cylindrical helical equipment. Using a helical equipment with a Globoid pinion is definitely common in lower cost in applications such as for example automotive electric powered gear actuators. The significant price advantage comes because of the probability to injection mold the helical plastic material gear. The load capacity of the simplified helical/Globoid transmission is decreased to the level below the load capacity of the standard worm gear. However the driving efficiency continues to be better compare to the standard worm gear.
There are simply a few suppliers of the Globoid gear. division of Textron, situated in Traverse Town, MI. The detailed details about procedures utilized at Cone Drive for manufacturing of its gear cannot be found. However, based on publicly released information it can be understood that the gear is produced by CNC milling with make use of a small ball shaped cutter.
Ever-power has capability to design, prototype and supply 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 gear CAD versions can be used in various CNC machining shops for generating globoid gear at considerably reduced cost.
Ever-power Globoid 3-dimentional CAD model.
It has to be noted that production of the Globoid equipment is more technical 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 cutting tool needs to be capable to tilt to be able to produce the enveloping form.
The newer production methods are under advancement. The most promising creation method of the Globoid pinion is certainly continues grinding process, which incorporates a grinding steering wheel (gemstone or CBN plated) with specific Ever-power simulated geometry. The complication of the novel procedure is the problems with simulation of the geometry of the grinding tool. The grinding tooth would have to generate a correct kind 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 making of 3-dimensional CAD types of grinding equipment for high volume creation of the Globoid items.
The most common use 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 already been made by grinding with a tilting grinding wheel. The Globoid gears have been cut by a special hub, which replicated the shape of the Globoid Pinion. Special machines for making the trimming hubs have been developed. Because the modern motor vehicle steering systems began to use traditional Bishop or advanced Ever-power variable ratio rack and pinion technology, the demand for the Globoid gears offers been reduced.
Variable ratio technology comparison
Vr-rack technology was introduced:
Before 2000
Underlying mathematical model is founded on:
Rack geometry calculation precision is:
Tied to the boundaries of the classic gear theory
Capacity to produce the vr-rack with not involute type for reduced noise
Capability to generate vr-rack with an increase of ratio gain is:
Cost of vr-rack style is:
Ever-power advanced Variable Ratio rack and pinion high ratio gain technology for electric motor sport racing applications.
Ever-power low noise Variable Ratio rack and pinion not involute technology.
Ever-power pioneered in developing of the next generation of Globoid gears. In 1999 Ever-power introduced a skew axis Globoid gear as a higher load capability and increased driving performance option to the classic Globoid equipment.
Ever-power skew axis (wormoid) gear.
It needs to be noted that the name WORMOID does not relate to any scientific term and it is a product of Dr. Stepan V. Lunin, who was simply the initial in proposing this style and, more importantly, he was the first 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 capability of the idea such as for example conjugated transmission action and significant boost 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 style and development of products predicated on Ever-power wormoid technology.
It needs to be noted that wormoid gear style from Ever-power is obviously promising unique advantages compare to the vintage Globoid (double enveloping) gear. 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 so the load on every individual tooth is reduced. The other apparent advantage is increase driving efficiency. As one can see, the part of the pinion with bigger diameter is driving the corresponding part of the gear, that includes a larger diameter aswell. Such of exclusive feature of Ever-power wormoid is usually missing in the classic Globoid gear and results in higher sliding velocities and higher friction drug on the traditional globoid gear. A skilled in the art engineer would immediately derive possible design benefits of the wormoid gear. For example, using of the wormoid gear can significantly reduce cost of electric powered help mechanisms that are commonly applied to modern automobiles. Because of the bigger driving efficiency, wormoid equipment set can be designed with increase ration and provide the same driving performance as the original worm or double enveloping worm equipment. 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 solution wormoid gear style from Ever-power would be capable to raise the ratio up to 30:1 and the torque on the gear up to 150 Hm without enhance of the center distance between the equipment and the pinion.


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