self locking gearbox

Worm gearboxes with countless combinations
Ever-Power offers a very wide variety of worm gearboxes. As a result of modular design the standard programme comprises countless combinations with regards to selection of equipment housings, mounting and interconnection options, flanges, shaft styles, kind of oil, surface therapies etc.
Sturdy and reliable
The design of the Ever-Power worm gearbox is easy and well proven. We simply use high self locking gearbox quality components such as properties in cast iron, lightweight aluminum and stainless, worms in the event hardened and polished metal and worm tires in high-quality bronze of particular alloys ensuring the optimum wearability. The seals of the worm gearbox are given with a dust lip which efficiently resists dust and drinking water. In addition, the gearboxes will be greased for life 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 decrease. An comparative gearing with the same equipment ratios and the same transferred electrical power is bigger when compared to a worm gearing. Meanwhile, the worm gearbox is usually in a more simple design.
A double reduction may be composed of 2 common gearboxes or as a particular gearbox.
Compact design
Compact design is one of the key words of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or special gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is because of the very smooth operating of the worm gear combined with the use of cast iron and great precision on aspect manufacturing and assembly. Regarding the our accuracy gearboxes, we have extra health care of any sound which can be interpreted as a murmur from the apparatus. So the general noise degree of our gearbox can be reduced to a complete 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 benefit producing the incorporation of the gearbox substantially simpler and more compact.The worm gearbox can be an angle gear. This can often be an advantage for incorporation into constructions.
Strong bearings in stable housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the gear house and is perfect for immediate suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Electric power worm gearboxes will provide a self-locking result, which in lots of situations can be utilised as brake or as extra secureness. As well spindle gearboxes with a trapezoidal spindle are self-locking, making them well suited for an array of solutions.
In most equipment drives, when driving torque is suddenly reduced as a result of electricity off, torsional vibration, vitality 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 gravity, springtime load, etc. The latter state is called backdriving. During inertial motion or backdriving, the powered output shaft (load) turns into the traveling one and the traveling input shaft (load) turns into the powered one. There are many gear drive applications where result shaft driving is undesirable. To be able to prevent it, several types of brake or clutch units are used.
However, there are also solutions in the apparatus transmitting that prevent inertial action or backdriving using self-locking gears without any additional products. The most common one is a worm equipment with a minimal lead angle. In self-locking worm gears, torque utilized from the load side (worm gear) is blocked, i.e. cannot travel the worm. However, their application comes with some restrictions: the crossed axis shafts’ arrangement, relatively high gear ratio, low speed, low gear mesh effectiveness, increased heat technology, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can use any gear ratio from 1:1 and bigger. They have the driving mode and self-locking function, when the inertial or backdriving torque is usually put on the output gear. Initially these gears had suprisingly low ( <50 percent) driving effectiveness that limited their application. Then it was proved [3] that high driving efficiency of these kinds of gears is possible. Requirements of the self-locking was analyzed in the following paragraphs [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 distinct applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents regular gears (a) and self-locking gears (b), in case of inertial driving. Practically all conventional equipment drives possess the pitch point P located in the active part the contact brand B1-B2 (Figure 1a and Shape 2a). This pitch stage location provides low specific sliding velocities and friction, and, consequently, high driving effectiveness. In case when this kind of gears are driven by output load or inertia, they are rotating freely, as the friction moment (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, applied to the pinion
F - driving force
F’ - driving 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 lively portion the contact line B1-B2. There are two options. Choice 1: when the point P is placed between a middle of the pinion O1 and the idea B2, where the outer diameter of the gear intersects the contact line. This makes the self-locking possible, however the driving productivity will be low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the idea P is put between the point B1, where the outer size of the pinion intersects the collection contact and a center of the gear O2. This kind of gears can be self-locking with relatively huge driving productivity > 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 second (torque) T’1 = F’ x L’1, where L’1 is definitely a lever of the drive F’1. This condition could be presented 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 position at the end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot be fabricated with the requirements tooling with, for example, the 20o pressure and rack. This makes them incredibly suited to Direct Gear Style® [5, 6] that delivers required gear functionality and after that defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth produced by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is shaped by two involutes of two several base circles (Figure 3b). The tooth idea circle da allows avoiding the pointed tooth hint. The equally spaced the teeth form the gear. The fillet account between teeth was created independently to avoid interference and offer minimum bending anxiety. The working pressure angle aw and the speak to 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
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 contact. If the sliding friction coefficient f = 0.1 - 0.3, it needs the transverse operating pressure angle to aw = 75 - 85o. Because of this, the transverse get in touch with ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse get in touch with ratio should be compensated by the axial (or face) get in touch with ratio eb to ensure the total speak to ratio eg = ea + eb ≥ 1.0. This is often attained by employing helical gears (Shape 4). However, helical gears apply the axial (thrust) power on the gear bearings. The double helical (or “herringbone”) gears (Determine 4) allow to compensate this force.
Substantial transverse pressure angles bring about increased bearing radial load that could be up to four to five occasions higher than for the conventional 20o pressure angle gears. Bearing variety and gearbox housing design should be done accordingly to hold this elevated load without excessive deflection.
Program of the asymmetric tooth for unidirectional drives allows for improved functionality. For the self-locking gears that are being used to avoid backdriving, the same tooth flank is employed for both generating and locking modes. In cases like this asymmetric tooth profiles give much higher transverse speak to ratio at the provided pressure angle compared to the symmetric tooth flanks. It creates it possible to lessen the helix position and axial bearing load. For the self-locking gears which used to avoid inertial driving, diverse tooth flanks are being used for traveling and locking modes. In this case, asymmetric tooth account with low-pressure position provides high effectiveness for driving method and the contrary high-pressure angle tooth profile is utilized for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype pieces were made predicated on the developed mathematical designs. The gear info are offered in the Table 1, and the check gears are shown in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric engine was used to operate a vehicle the actuator. An integrated swiftness and torque sensor was attached on the high-swiftness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low speed shaft of the gearbox via coupling. The suggestions and productivity torque and speed details were captured in the data acquisition tool and further analyzed in a pc using data analysis application. The instantaneous effectiveness of the actuator was calculated and plotted for an array of speed/torque combination. Standard driving productivity of the self- locking gear obtained during evaluating was above 85 percent. The self-locking house of the helical gear occur backdriving mode was likewise tested. During this test the external torque was applied to the output gear shaft and the angular transducer demonstrated no angular movements of source shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. Even so, this type of gears has many potential applications in lifting mechanisms, assembly tooling, and other gear drives where the backdriving or inertial traveling is not permissible. Among such app [7] of the self-locking gears for a constantly variable valve lift system was suggested for an vehicle engine.
In this paper, a principle of work of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and testing of the gear prototypes has proved comparatively high driving productivity and dependable self-locking. The self-locking gears may find many applications in a variety of industries. For example, in a control devices where position stability is vital (such as in vehicle, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to achieve required performance. Similar to the worm self-locking gears, the parallel axis self-locking gears are delicate to operating conditions. The locking dependability is influenced by lubrication, vibration, misalignment, etc. Implementation of these gears should be finished with caution and needs comprehensive testing in every possible operating conditions.

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