Worm gearboxes with many combinations
Ever-Power offers an extremely broad range of worm gearboxes. Due to the modular design the standard programme comprises many combinations in terms of selection of equipment housings, mounting and connection options, flanges, shaft styles, kind of oil, surface remedies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is simple and well proven. We only use top quality components such as houses in cast iron, aluminum and stainless steel, worms in case hardened and polished metal and worm tires in high-quality bronze of particular alloys ensuring the the best possible wearability. The seals of the worm gearbox are given with a dirt lip which effectively resists dust and water. Furthermore, the gearboxes will be greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes allow for reductions as high as 100:1 in one step or 10.000:1 in a double decrease. An comparative gearing with the same gear ratios and the same transferred electrical power is bigger than a worm gearing. On the other hand, the worm gearbox is in a far more simple design.
A double reduction could be composed of 2 standard gearboxes or as a particular gearbox.
Compact design
Compact design is among the key words of the typical gearboxes of the Ever-Power-Series. Further optimisation can be achieved through the use of adapted gearboxes or specialized gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is because of the very smooth jogging of the worm gear combined with the utilization of cast iron and great precision on component manufacturing and assembly. Regarding the our precision gearboxes, we consider extra attention of any sound which can be interpreted as a murmur from the gear. Therefore the general noise level of our gearbox can be reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This generally proves to become a decisive advantage producing the incorporation of the gearbox significantly simpler and smaller sized.The worm gearbox can be an angle gear. This is often an advantage for incorporation into constructions.
Strong bearings in sturdy housing
The output shaft of the Ever-Power worm gearbox is very firmly embedded in the gear house and is suitable for direct suspension for wheels, movable arms and other parts rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes will provide a self-locking impact, which in many situations works extremely well as brake or as extra security. As well spindle gearboxes with a trapezoidal spindle will be self-locking, making them ideal for a variety of solutions.
In most equipment drives, when driving torque is suddenly reduced consequently of electricity off, torsional vibration, electricity outage, or any mechanical failure at the tranny input area, then gears will be rotating either in the same route driven by the system inertia, or in the contrary route driven by the resistant output load due to gravity, planting season load, etc. The latter condition is called backdriving. During inertial motion or backdriving, the motivated output shaft (load) becomes the traveling one and the driving input shaft (load) turns into the powered one. There are plenty of gear drive applications where outcome shaft driving is unwanted. As a way to prevent it, several types of brake or clutch products are used.
However, additionally, there are solutions in the apparatus transmitting that prevent inertial action or backdriving using self-locking gears with no additional products. The most frequent one is normally a worm gear with a minimal lead angle. In self-locking worm gears, torque utilized from the load side (worm equipment) is blocked, i.electronic. cannot drive the worm. Nevertheless, their application comes with some restrictions: the crossed axis shafts' arrangement, relatively high gear ratio, low rate, low gear mesh performance, increased heat technology, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can use any equipment ratio from 1:1 and larger. They have the traveling mode and self-locking setting, when the inertial or backdriving torque is certainly applied to the output gear. Originally these gears had suprisingly low ( Self-Locking Condition
Determine 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents conventional gears (a) and self-locking gears (b), in the event of inertial driving. Practically all conventional equipment drives possess the pitch stage P located in the active portion the contact series B1-B2 (Figure 1a and Number 2a). This pitch point location provides low certain sliding velocities and friction, and, due to this fact, high driving efficiency. In case when such gears are driven by end result load or inertia, they will be rotating freely, as the friction moment (or torque) is not 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, put on the pinion
F – driving force
F' – driving force, when the backdriving or perhaps inertial torque put on the gear
aw – operating transverse pressure angle
g – arctan(f) – friction angle
f – average friction coefficient
In order to make gears self-locking, the pitch point P should be located off the energetic portion the contact line B1-B2. There happen to be two options. Alternative 1: when the idea P is positioned between a centre of the pinion O1 and the idea B2, where the outer size of the gear intersects the contact series. This makes the self-locking possible, but the driving productivity will end up being low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the idea P is placed between your point B1, where the outer size of the pinion intersects the brand contact and a middle of the gear O2. This sort of gears could be self-locking with relatively huge driving efficiency > 50 percent.
Another condition of self-locking is to truly have a ample friction angle g to deflect the force F' beyond the guts of the pinion O1. It creates the resisting self-locking point in time (torque) T'1 = F' x L'1, where L'1 is usually a lever of the push F'1. This condition could be offered as L'1min > 0 or
(1) Equation 1
or
(2) Equation 2
where:
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear quantity of teeth,
– involute profile position at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears 
are customized. They cannot end up being fabricated with the standards tooling with, for instance, the 20o pressure and rack. This makes them extremely well suited for Direct Gear Design® [5, 6] that provides required gear overall performance and from then on defines tooling parameters.
Direct Gear Style presents the symmetric equipment tooth created by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is shaped by two involutes of two several base circles (Figure 3b). The tooth tip circle da allows avoiding the pointed tooth hint. The equally spaced teeth form the apparatus. The fillet profile between teeth is designed independently in order to avoid interference and provide self locking gearbox minimum bending stress. 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 needs the transverse operating pressure position to aw = 75 – 85o. As a result, the transverse contact ratio ea High transverse pressure angles bring about increased bearing radial load that may be up to four to five times higher than for the traditional 20o pressure angle gears. Bearing selection and gearbox housing style ought to be done accordingly to hold this elevated load without excessive deflection.
Request of the asymmetric tooth for unidirectional drives allows for improved functionality. For the self-locking gears that are used to avoid backdriving, the same tooth flank is utilized for both traveling and locking modes. In this instance asymmetric tooth profiles present much higher transverse contact ratio at the presented pressure angle than the symmetric tooth flanks. It creates it possible to reduce the helix position and axial bearing load. For the self-locking gears that used to avoid inertial driving, different tooth flanks are being used for traveling and locking modes. In cases like this, asymmetric tooth account with low-pressure angle provides high effectiveness for driving setting and the opposite high-pressure angle tooth profile is employed for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype sets were made predicated on the developed mathematical models. The gear info are offered in the Table 1, and the test gears are offered in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric motor was used to operate a vehicle the actuator. A velocity and torque sensor was mounted on the high-swiftness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low velocity shaft of the gearbox via coupling. The suggestions and end result torque and speed information were captured in the info acquisition tool and additional analyzed in a computer applying data analysis program. The instantaneous performance of the actuator was calculated and plotted for a broad range of speed/torque combination. Common driving proficiency of the self- locking equipment obtained during screening was above 85 percent. The self-locking house of the helical gear occur backdriving mode was also tested. In this test the external torque was put on the output equipment shaft and the angular transducer revealed no angular activity of insight shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. Even so, this kind of gears has many potential applications in lifting mechanisms, assembly tooling, and other equipment drives where in fact the backdriving or inertial traveling is not permissible. Among such request [7] of the self-locking gears for a continuously variable valve lift program was recommended for an automobile engine.
Summary
In this paper, a theory of job of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and tests of the gear prototypes has proved comparatively high driving effectiveness and dependable self-locking. The self-locking gears could find many applications in various industries. For example, in a control systems where position steadiness is essential (such as for example in motor vehicle, 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 very sensitive to operating conditions. The locking dependability is damaged by lubrication, vibration, misalignment, etc. Implementation of the gears should be done with caution and requires comprehensive testing in all possible operating conditions.
