Worm gearboxes with countless combinations
Ever-Power offers an extremely wide range of worm gearboxes. As a result of modular design the standard programme comprises many combinations in terms of selection of equipment housings, mounting and interconnection options, flanges, shaft designs, kind of oil, surface treatment options etc.
Sturdy and reliable
The design of the Ever-Power worm gearbox is easy and well proven. We simply use high quality components such as properties in cast iron, lightweight aluminum and stainless steel, worms in case hardened and polished metal and worm tires in high-quality bronze of particular alloys ensuring the maximum wearability. The seals of the worm gearbox are provided with a dirt lip which properly resists dust and drinking water. Furthermore, the gearboxes will be greased forever with synthetic oil.
Large reduction 100:1 in one step
As default the worm gearboxes enable reductions as high as 100:1 in one step or 10.000:1 in a double reduction. An equivalent gearing with the same gear ratios and the same transferred vitality is bigger than a worm gearing. In the mean time, the worm gearbox is definitely in a far more simple design.
A double reduction could be composed of 2 typical gearboxes or as a special gearbox.
Compact design
Compact design is among the key terms of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or exceptional gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is due to the very simple working of the worm gear combined with the application of cast iron and high precision on component manufacturing and assembly. In connection with our precision gearboxes, we have extra health care of any sound which can be interpreted as a murmur from the apparatus. Therefore the general noise degree of our gearbox is reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to each other. This often proves to become a decisive advantages producing the incorporation of the gearbox substantially 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 very firmly embedded in the apparatus house and is suitable for direct suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Electricity worm gearboxes will provide a self-locking result, which in many situations can be utilised as brake or as extra reliability. Likewise spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them ideal for a variety of solutions.
In most gear drives, when traveling torque is suddenly reduced therefore of electrical power off, torsional vibration, ability outage, or any mechanical failing at the tranny input aspect, then gears will be rotating either in the same direction driven by the system inertia, or in the contrary way driven by the resistant output load because of gravity, spring load, etc. The latter condition is called backdriving. During inertial movement or backdriving, the driven output shaft (load) turns into the generating one and the generating input shaft (load) turns into the powered one. There are several gear drive applications where end result shaft driving is unwanted. So that you can prevent it, different types of brake or clutch products are used.
However, additionally, there are solutions in the 
gear transmission that prevent inertial movement or backdriving using self-locking gears with no additional gadgets. The most typical one is normally a worm gear with a minimal lead angle. In self-locking worm gears, torque utilized from the load side (worm gear) is blocked, i.electronic. cannot drive the worm. Nevertheless, their application includes some restrictions: the crossed axis shafts’ arrangement, relatively high gear ratio, low acceleration, low gear mesh efficiency, increased heat generation, 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 larger. They have the generating mode and self-locking setting, when the inertial or backdriving torque is normally applied to the output gear. Primarily these gears had very low ( <50 percent) traveling effectiveness that limited their app. Then it was proved [3] that huge driving efficiency of these kinds of gears is possible. Conditions of the self-locking was analyzed in this posting [4]. This paper explains the basic principle of the self-locking process for the parallel axis gears with symmetric and asymmetric tooth profile, and displays their suitability for unique applications.
Self-Locking Condition
Shape 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents standard gears (a) and self-locking gears (b), in case of inertial driving. Almost all conventional equipment drives possess the pitch level P located in the active portion the contact line B1-B2 (Figure 1a and Number 2a). This pitch stage location provides low particular sliding velocities and friction, and, therefore, high driving performance. In case when this kind of gears are powered by end result load or inertia, they happen to 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, put on 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 ought to be located off the lively portion the contact line B1-B2. There happen to be two options. Choice 1: when the point P is positioned between a centre of the pinion O1 and the idea B2, where in fact the outer diameter of the gear intersects the contact brand. This makes the self-locking possible, but the driving effectiveness will always be low under 50 percent [3]. Option 2 (figs 1b and 2b): when the idea P is positioned between your point B1, where in fact the outer size of the pinion intersects the range contact and a middle of the apparatus O2. This sort of gears can be self-locking with relatively huge driving efficiency > 50 percent.
Another condition of self-locking is to have a sufficient friction angle g to deflect the force F’ beyond the center of the pinion O1. It generates the resisting self-locking minute (torque) T’1 = F’ x L’1, where L’1 is a lever of the force F’1. This condition can be shown as L’1min > 0 or
(1) Equation 1
or
(2) Equation 2
where:
u = n2/n1 – gear ratio,
n1 and n2 – pinion and gear amount of teeth,
– involute profile angle at the end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot end up being self locking gearbox fabricated with the requirements tooling with, for instance, the 20o pressure and rack. This makes them incredibly well suited for Direct Gear Style® [5, 6] that delivers required gear functionality and after that defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth shaped by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is produced by two involutes of two numerous base circles (Figure 3b). The tooth idea circle da allows avoiding the pointed tooth hint. The equally spaced tooth form the gear. The fillet account between teeth was created independently to avoid interference and offer minimum bending pressure. The operating pressure angle aw and the contact ratio ea are identified by the next 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 substantial sliding friction in the tooth speak to. 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 get in touch with ratio ought to be compensated by the axial (or face) contact ratio eb to ensure the total speak to ratio eg = ea + eb ≥ 1.0. This could be achieved by using helical gears (Physique 4). Even so, helical gears apply the axial (thrust) push on the gear bearings. The dual helical (or “herringbone”) gears (Number 4) allow to pay this force.
Huge transverse pressure angles lead to increased bearing radial load that could be up to four to five moments higher than for the traditional 20o pressure angle gears. Bearing variety and gearbox housing design ought to be done accordingly to carry this increased load without unnecessary deflection.
Program of the asymmetric tooth for unidirectional drives permits improved performance. For the self-locking gears that are used to prevent backdriving, the same tooth flank is used for both generating and locking modes. In cases like this asymmetric tooth profiles present much higher transverse get in touch with ratio at the presented pressure angle compared to the symmetric tooth flanks. It makes it possible to reduce the helix angle and axial bearing load. For the self-locking gears that used to avoid inertial driving, unique tooth flanks are being used for traveling and locking modes. In this case, asymmetric tooth profile with low-pressure angle provides high efficiency for driving mode and the opposite high-pressure angle tooth account is employed for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype pieces were made predicated on the developed mathematical versions. The gear info are shown in the Table 1, and the check gears are presented in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric electric motor was used to drive the actuator. A built-in velocity and torque sensor was mounted on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low swiftness shaft of the gearbox via coupling. The insight and outcome torque and speed details were captured in the info acquisition tool and further analyzed in a computer employing data analysis application. The instantaneous productivity of the actuator was calculated and plotted for a variety of speed/torque combination. Average driving performance of the personal- locking gear obtained during assessment was above 85 percent. The self-locking home of the helical equipment occur backdriving mode was also tested. During this test the external torque was applied to the output equipment shaft and the angular transducer confirmed no angular movement of insight shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears were used in textile industry [2]. Nevertheless, this kind of gears has a large number of potential applications in lifting mechanisms, assembly tooling, and other gear drives where in fact the backdriving or inertial driving is not permissible. Among such app [7] of the self-locking gears for a constantly variable valve lift system was advised for an auto engine.
Summary
In this paper, a theory of operate of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and assessment of the gear prototypes has proved relatively high driving performance and reputable self-locking. The self-locking gears could find many applications in various industries. For instance, in a control systems where position steadiness is essential (such as for example in auto, aerospace, medical, robotic, agricultural etc.) the self-locking allows to accomplish required performance. Like the worm self-locking gears, the parallel axis self-locking gears are delicate to operating circumstances. The locking dependability is afflicted by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and requires comprehensive testing in all possible operating conditions.