Worm gearboxes with many combinations
Ever-Power offers a very wide variety of worm gearboxes. Because of the modular design the typical programme comprises countless combinations in terms of selection of equipment housings, mounting and interconnection options, flanges, shaft designs, type of oil, surface solutions 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 houses in cast iron, aluminum and stainless steel, worms in the event hardened and polished steel and worm wheels in high-quality bronze of special alloys ensuring the optimum wearability. The seals of the worm gearbox are provided with a dust lip which effectively resists dust and water. Furthermore, the gearboxes are greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes allow for 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 than a worm gearing. At the same time, the worm gearbox is normally in a far more simple design.
A double reduction could be composed of 2 normal gearboxes or as a particular gearbox.
Compact design
Compact design is among the key phrases of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or particular gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is due to the very smooth operating of the worm gear combined with the consumption of cast iron and substantial precision on part manufacturing and assembly. Regarding the our accuracy gearboxes, we have extra treatment of any sound that can be interpreted as a murmur from the apparatus. Therefore the general noise degree of our gearbox is definitely reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This sometimes proves to become a decisive benefits making the incorporation of the gearbox considerably simpler and smaller sized.The worm gearbox can be an angle gear. This is normally an advantage for incorporation into constructions.
Strong bearings in sturdy housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the gear house and is ideal for direct suspension for wheels, movable arms and other areas rather than having to build a separate suspension.
Self locking
For larger gear ratios, Ever-Electric power worm gearboxes provides a self-locking impact, which in lots of situations can be utilized as brake or as extra reliability. As well spindle gearboxes with a trapezoidal spindle will be self-locking, making them perfect for a 
broad range of solutions.
In most equipment drives, when traveling torque is suddenly reduced because of this of vitality off, torsional vibration, electricity outage, or any mechanical failing at the transmission input side, then gears will be rotating either in the same way driven by the machine inertia, or in the opposite way driven by the resistant output load due to self locking gearbox gravity, springtime load, etc. The latter condition is known as backdriving. During inertial action or backdriving, the motivated output shaft (load) turns into the traveling one and the generating input shaft (load) turns into the driven one. There are various gear drive applications where output shaft driving is undesirable. To be able to prevent it, various kinds of brake or clutch equipment are used.
However, there are also solutions in the gear transmission that prevent inertial movement or backdriving using self-locking gears with no additional units. The most common one can be a worm equipment with a low lead angle. In self-locking worm gears, torque applied from the load side (worm equipment) is blocked, i.electronic. cannot travel the worm. Even so, their application includes some restrictions: the crossed axis shafts’ arrangement, relatively high gear ratio, low acceleration, low gear mesh efficiency, increased heat era, etc.
Also, there will be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can make use of any equipment ratio from 1:1 and bigger. They have the generating mode and self-locking mode, when the inertial or backdriving torque is definitely applied to the output gear. Initially these gears had suprisingly low ( <50 percent) generating efficiency that limited their app. Then it had been proved [3] that high driving efficiency of such gears is possible. Conditions of the self-locking was analyzed in this posting [4]. This paper explains the theory of the self-locking procedure for the parallel axis gears with symmetric and asymmetric pearly whites profile, and shows their suitability for diverse applications.
Self-Locking Condition
Shape 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents typical gears (a) and self-locking gears (b), in the event of inertial driving. Pretty much all conventional gear drives possess the pitch level P situated in the active portion the contact line B1-B2 (Figure 1a and Physique 2a). This pitch level location provides low particular sliding velocities and friction, and, consequently, high driving efficiency. In case when this kind of gears are motivated by productivity load or inertia, they will be rotating freely, because the friction instant (or torque) isn’t sufficient to avoid 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, applied to the pinion
F – driving force
F’ – generating force, when the backdriving or 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 should be located off the dynamic portion the contact line B1-B2. There are two options. Option 1: when the point P is placed between a middle of the pinion O1 and the idea B2, where in fact the outer diameter of the apparatus intersects the contact series. This makes the self-locking possible, but the driving efficiency will be low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the point P is located between your point B1, where the outer size of the pinion intersects the line contact and a middle of the apparatus O2. This type of gears can be self-locking with relatively large driving proficiency > 50 percent.
Another condition of self-locking is to have a satisfactory friction angle g to deflect the force F’ beyond the guts of the pinion O1. It creates the resisting self-locking instant (torque) T’1 = F’ x L’1, where L’1 can be a lever of the force F’1. This condition could be presented as L’1min > 0 or
(1) Equation 1
or
(2) Equation 2
where:
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear amount of teeth,
– involute profile angle at the end of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot become fabricated with the standards tooling with, for example, the 20o pressure and rack. This makes them very ideal for Direct Gear Style® [5, 6] that provides required gear functionality and from then on defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth created by two involutes of 1 base circle (Figure 3a). The asymmetric gear tooth is produced by two involutes of two several base circles (Figure 3b). The tooth idea circle da allows avoiding the pointed tooth suggestion. The equally spaced the teeth form the apparatus. The fillet account between teeth is designed independently to avoid interference and provide minimum bending stress. The operating pressure angle aw and the speak to 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
where:
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 contact. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure angle to aw = 75 – 85o. Consequently, the transverse contact ratio ea < 1.0 (typically 0.4 - 0.6). Insufficient the transverse contact ratio ought to be compensated by the axial (or face) get in touch with ratio eb to guarantee the total contact ratio eg = ea + eb ≥ 1.0. This is often achieved by using helical gears (Physique 4). On the other hand, helical gears apply the axial (thrust) pressure on the gear bearings. The twice helical (or “herringbone”) gears (Body 4) allow to pay this force.
Great transverse pressure angles cause increased bearing radial load that could be up to four to five circumstances higher than for the conventional 20o pressure angle gears. Bearing collection and gearbox housing design should be done accordingly to hold this increased load without excessive deflection.
Program of the asymmetric tooth for unidirectional drives permits improved efficiency. For the self-locking gears that are being used to avoid backdriving, the same tooth flank can be used for both generating and locking modes. In this case asymmetric tooth profiles offer much higher transverse speak to ratio at the presented 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 avoid inertial driving, several tooth flanks are used for driving and locking modes. In cases like this, asymmetric tooth account with low-pressure angle provides high performance for driving setting and the contrary high-pressure angle tooth profile is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype pieces were made based on the developed mathematical models. The gear data are offered in the Desk 1, and the test gears are provided in Figure 5.
The schematic presentation of the test setup is demonstrated in Figure 6. The 0.5Nm electric electric motor was used to operate a vehicle the actuator. A rate and torque sensor was attached on the high-acceleration shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low swiftness shaft of the gearbox via coupling. The source and end result torque and speed details were captured in the data acquisition tool and additional analyzed in a pc using data analysis application. The instantaneous efficiency of the actuator was calculated and plotted for a variety of speed/torque combination. Typical driving effectiveness of the personal- locking equipment obtained during assessment was above 85 percent. The self-locking house of the helical equipment occur backdriving mode was also tested. In this test the external torque was applied to the output gear shaft and the angular transducer demonstrated no angular motion of type shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were used in textile industry [2]. Nevertheless, this kind of gears has various potential applications in lifting mechanisms, assembly tooling, and other gear drives where in fact the backdriving or inertial generating is not permissible. One of such software [7] of the self-locking gears for a continuously variable valve lift program was advised for an car engine.
Summary
In this paper, a basic principle of do the job of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and assessment of the gear prototypes has proved fairly high driving performance and reputable self-locking. The self-locking gears could find many applications in a variety of industries. For instance, in a control systems where position balance is essential (such as in vehicle, aerospace, medical, robotic, agricultural etc.) the self-locking allows to achieve required performance. Like the worm self-locking gears, the parallel axis self-locking gears are very sensitive to operating conditions. The locking reliability is afflicted by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and requires comprehensive testing in every possible operating conditions.
