Worm gearboxes with many combinations
Ever-Power offers an extremely wide range of worm gearboxes. Due to the modular design the typical programme comprises countless combinations in terms of selection of equipment housings, mounting and connection options, flanges, shaft patterns, kind of oil, surface treatment options etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is easy and well proven. We only use high quality components such as properties in cast iron, aluminum and stainless, worms in the event hardened and polished steel and worm wheels in high-quality bronze of special alloys ensuring the the best wearability. The seals of the worm gearbox are provided with a dirt lip which properly resists dust and drinking water. Furthermore, the gearboxes are greased forever with synthetic oil.
Large reduction 100:1 in one step
As default the worm gearboxes enable reductions of up to 100:1 in one single step or 10.000:1 in a double reduction. An equivalent gearing with the same gear ratios and the same transferred electricity is bigger when compared to a worm gearing. Meanwhile, the worm gearbox is definitely in a more simple design.
A double reduction could be composed of 2 standard gearboxes or as a particular gearbox.
Compact design is among the key terms of the standard gearboxes of the Ever-Power-Series. Further optimisation can be achieved through the use of adapted gearboxes or distinctive gearboxes.
Our worm gearboxes and actuators are really quiet. This is due to the very smooth running of the worm gear combined with the usage of cast iron and huge precision on component manufacturing and assembly. In connection with our precision gearboxes, we have extra care and attention of any sound that can be interpreted as a murmur from the gear. So the general noise degree of our gearbox is definitely reduced to an absolute minimum.
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This typically proves to be a decisive advantage making the incorporation of the gearbox considerably simpler and more compact.The worm gearbox is an angle gear. This is normally an advantage for incorporation into constructions.
Strong bearings in solid housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the self locking gearbox apparatus house and is perfect for immediate suspension for wheels, movable arms and other areas rather than having to create a separate suspension.
For larger gear ratios, Ever-Ability worm gearboxes will provide a self-locking impact, which in many situations can be used as brake or as extra security. Likewise spindle gearboxes with a trapezoidal spindle are self-locking, making them well suited for a wide variety of solutions.
In most equipment drives, when generating torque is suddenly reduced because of this of vitality off, torsional vibration, electrical power outage, or any mechanical failure at the tranny input aspect, then gears will be rotating either in the same route driven by the system inertia, or in the contrary way driven by the resistant output load because of gravity, springtime load, etc. The latter state is called backdriving. During inertial motion or backdriving, the influenced output shaft (load) turns into the traveling one and the traveling input shaft (load) becomes the powered one. There are numerous gear drive applications where result shaft driving is unwanted. To be able to prevent it, different types of brake or clutch products are used.
However, there are also solutions in the gear transmission that prevent inertial action or backdriving using self-locking gears with no additional units. The most typical one can be a worm gear with a minimal lead angle. In self-locking worm gears, torque used from the load side (worm equipment) is blocked, i.electronic. cannot drive the worm. Nevertheless, their application comes with some constraints: the crossed axis shafts’ arrangement, relatively high gear ratio, low quickness, low gear mesh efficiency, increased heat era, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can use any gear ratio from 1:1 and higher. They have the generating mode and self-locking setting, when the inertial or backdriving torque is definitely applied to the output gear. Primarily these gears had suprisingly low ( <50 percent) driving performance that limited their request. Then it was proved  that huge driving efficiency of such gears is possible. Requirements of the self-locking was analyzed in the following paragraphs . This paper explains the basic principle of the self-locking process for the parallel axis gears with symmetric and asymmetric teeth profile, and displays their suitability for diverse applications.
Body 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents regular gears (a) and self-locking gears (b), in the event of inertial driving. Virtually all conventional gear drives possess the pitch stage P situated in the active part the contact series B1-B2 (Figure 1a and Shape 2a). This pitch stage location provides low particular sliding velocities and friction, and, therefore, high driving efficiency. In case when this kind of gears are powered by outcome load or inertia, they happen to be rotating freely, as the friction minute (or torque) is not sufficient to stop rotation. In Figure 1 and Figure 2:
1- Driving pinion
2 – Driven gear
db1, db2 – base diameters
dp1, dp2 – pitch diameters
da1, da2 – outer diameters
T1 – driving pinion torque
T2 – driven gear torque
T’2 – driving torque, applied to the gear
T’1 – driven torque, put on the pinion
F – driving force
F’ – traveling force, when the backdriving or perhaps inertial torque applied to the gear
aw – operating transverse pressure angle
g – arctan(f) – friction angle
f – average friction coefficient
To make gears self-locking, the pitch point P ought to be located off the dynamic portion the contact line B1-B2. There are two options. Choice 1: when the idea P is positioned between a center of the pinion O1 and the idea B2, where the outer diameter of the apparatus intersects the contact range. This makes the self-locking possible, however the driving performance will end up being low under 50 percent . Option 2 (figs 1b and 2b): when the idea P is located between your point B1, where in fact the outer size of the pinion intersects the collection contact and a centre of the gear O2. This type of gears can be self-locking with relatively large driving performance > 50 percent.
Another condition of self-locking is to truly have a adequate friction angle g to deflect the force F’ beyond the center of the pinion O1. It creates the resisting self-locking minute (torque) T’1 = F’ x L’1, where L’1 can be a lever of the force F’1. This condition can be provided as L’1min > 0 or
(1) Equation 1
(2) Equation 2
u = n2/n1 – gear ratio,
n1 and n2 – pinion and gear number of teeth,
– involute profile angle at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot be fabricated with the standards tooling with, for example, the 20o pressure and rack. This makes them extremely suited to Direct Gear Style® [5, 6] that provides required gear functionality and from then on defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth formed by two involutes of 1 base circle (Figure 3a). The asymmetric gear tooth is shaped by two involutes of two several base circles (Figure 3b). The tooth suggestion circle da allows preventing the pointed tooth hint. The equally spaced tooth form the apparatus. The fillet account between teeth is designed independently to avoid interference and offer minimum bending stress. The working pressure angle aw and the get in touch with ratio ea are defined by the following formulae:
– for gears with symmetric teeth
(3) Equation 3
(4) Equation 4
– for gears with asymmetric teeth
(5) Equation 5
(6) Equation 6
(7) Equation 7
inv(x) = tan x – x – involute function of the profile angle x (in radians).
Conditions (1) and (2) show that self-locking requires ruthless and high sliding friction in the tooth get in touch with. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure position to aw = 75 – 85o. Due to this fact, the transverse get in touch with ratio ea < 1.0 (typically 0.4 - 0.6). Insufficient the transverse contact ratio ought to be compensated by the axial (or face) contact ratio eb to ensure the total get in touch with ratio eg = ea + eb ≥ 1.0. This can be achieved by applying helical gears (Physique 4). On the other hand, helical gears apply the axial (thrust) induce on the gear bearings. The dual helical (or “herringbone”) gears (Physique 4) allow to pay this force.
High transverse pressure angles cause increased bearing radial load that could be up to four to five moments higher than for the conventional 20o pressure angle gears. Bearing assortment and gearbox housing style ought to be done accordingly to carry this increased load without excessive deflection.
Application of the asymmetric teeth for unidirectional drives allows for improved effectiveness. For the self-locking gears that are used to prevent backdriving, the same tooth flank is utilized for both generating and locking modes. In cases like this asymmetric tooth profiles offer much higher transverse contact ratio at the given pressure angle compared to the symmetric tooth flanks. It makes it possible to reduce the helix position and axial bearing load. For the self-locking gears which used to prevent inertial driving, different tooth flanks are used for driving and locking modes. In this case, asymmetric tooth profile with low-pressure position provides high efficiency for driving mode and the contrary high-pressure angle tooth account is utilized for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype pieces were made based on the developed mathematical products. The gear data are provided in the Table 1, and the test gears are presented in Figure 5.
The schematic presentation of the test setup is shown in Figure 6. The 0.5Nm electric motor was used to drive the actuator. An integrated swiftness and torque sensor was installed on the high-acceleration shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low swiftness shaft of the gearbox via coupling. The source and result torque and speed info had been captured in the info acquisition tool and additional analyzed in a computer employing data analysis application. The instantaneous proficiency of the actuator was calculated and plotted for a variety of speed/torque combination. Normal driving proficiency of the self- locking equipment obtained during assessment was above 85 percent. The self-locking house of the helical gear set in backdriving mode was likewise tested. During this test the external torque was applied to the output equipment shaft and the angular transducer demonstrated no angular movement of insight shaft, which confirmed the self-locking condition.
Initially, self-locking gears were used in textile industry . Even so, this kind of gears has various potential applications in lifting mechanisms, assembly tooling, and other equipment drives where in fact the backdriving or inertial driving is not permissible. Among such program  of the self-locking gears for a constantly variable valve lift program was advised for an automobile engine.
In this paper, a theory of function of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and evaluating of the gear prototypes has proved fairly high driving efficiency and trustworthy self-locking. The self-locking gears may find many applications in various industries. For instance, in a control systems where position balance is essential (such as for example in vehicle, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to accomplish required performance. Like the worm self-locking gears, the parallel axis self-locking gears are sensitive to operating circumstances. The locking reliability is influenced by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and requires comprehensive testing in all possible operating conditions.
Worm gearboxes with many combinations