self locking gearbox

Worm gearboxes with countless combinations
Ever-Power offers an extremely wide selection 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, type of oil, surface procedures etc.
Sturdy and reliable
The design of the Ever-Power worm gearbox is simple and well proven. We just use high quality components such as residences in cast iron, light weight aluminum and stainless steel, worms in the event hardened and polished metal and worm wheels in high-quality bronze of particular alloys ensuring the the best wearability. The seals of the worm gearbox are given with a dirt lip which efficiently resists dust and drinking water. In addition, the gearboxes will be greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes enable reductions of up to 100:1 in one single step or 10.000:1 in a double decrease. An equivalent gearing with the same gear ratios and the same transferred vitality is bigger when compared to a worm gearing. Meanwhile, the worm gearbox is certainly in a far more simple design.
A double reduction could be composed of 2 regular gearboxes or as a special gearbox.
Compact design
Compact design is among the key words of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished through the use of adapted gearboxes or exceptional gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is due to the very soft running of the worm gear combined with the application of cast iron and substantial precision on component manufacturing and assembly. In connection with our accuracy gearboxes, we have extra proper care of any sound which can be interpreted as a murmur from the apparatus. So the general noise degree of our gearbox is definitely reduced to a complete minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to each other. This typically proves to be a decisive edge making the incorporation of the gearbox significantly simpler and more compact.The worm gearbox can be an angle gear. This is normally an edge for incorporation into constructions.
Strong bearings in sound housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the apparatus house and is ideal for direct suspension for wheels, movable arms and other areas rather than needing to create a separate suspension.
Self locking
For larger gear ratios, Ever-Electrical power worm gearboxes provides a self-locking result, which in many situations works extremely well as brake or as extra reliability. Also spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them perfect for a variety of solutions.
In most gear drives, when traveling torque is suddenly reduced consequently of electrical power off, torsional vibration, electrical power outage, or any mechanical failing at the transmitting input part, then gears will be rotating either in the same path driven by the machine inertia, or in the opposite way driven by the resistant output load due to gravity, early spring load, etc. The latter condition is called backdriving. During inertial action or backdriving, the motivated output shaft (load) becomes the generating one and the traveling input shaft (load) becomes the motivated one. There are plenty of gear drive applications where end 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 transmission that prevent inertial movement or backdriving using self-locking gears without any additional gadgets. The most frequent one is definitely a worm gear with a low lead angle. In self-locking worm gears, torque used from the strain side (worm gear) is blocked, i.electronic. cannot travel the worm. However, their application includes some limitations: the crossed axis shafts’ arrangement, relatively high equipment ratio, low acceleration, low gear mesh proficiency, increased heat technology, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can make use of any gear ratio from 1:1 and bigger. They have the driving mode and self-locking function, when the inertial or backdriving torque is normally applied to the output gear. At first these gears had very low ( <50 percent) generating productivity that limited their app. Then it had been proved [3] that great driving efficiency of this kind of gears is possible. Requirements of the self-locking was analyzed in the following paragraphs [4]. This paper explains the principle of the self-locking procedure 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 conventional gears (a) and self-locking gears (b), in the event of inertial driving. Practically all conventional equipment drives possess the pitch stage P situated in the active part the contact series B1-B2 (Figure 1a and Body 2a). This pitch point location provides low certain sliding velocities and friction, and, subsequently, high driving performance. In case when this kind of gears are influenced by result load or inertia, they will be rotating freely, as the friction instant (or torque) isn’t 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, put on the gear
T’1 – driven torque, applied to the pinion
F – driving force
F’ – generating 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
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. 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 gear intersects the contact range. This makes the self-locking possible, however the driving performance will be low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the idea P is placed between your point B1, where the outer diameter of the pinion intersects the brand contact and a center of the gear O2. This sort of gears can be self-locking with relatively great driving productivity > 50 percent.
Another condition of self-locking is to truly have a adequate friction angle g to deflect the force F’ beyond the guts of the pinion O1. It generates the resisting self-locking point in time (torque) T’1 = F’ x L’1, where L’1 is a lever of the force F’1. This condition could be offered as L’1min > 0 or
(1) self locking gearbox Equation 1
or
(2) Equation 2
where:
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear quantity of teeth,
– involute profile angle at the end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot always be fabricated with the benchmarks tooling with, for example, the 20o pressure and rack. This makes them extremely well suited for Direct Gear Design® [5, 6] that delivers required gear efficiency and after that defines tooling parameters.
Direct Gear Style presents the symmetric equipment tooth formed by two involutes of 1 base circle (Figure 3a). The asymmetric gear tooth is shaped by two involutes of two unique base circles (Figure 3b). The tooth suggestion circle da allows preventing the pointed tooth tip. The equally spaced pearly whites form the gear. The fillet profile between teeth was created independently to avoid interference and offer minimum bending tension. The operating pressure angle aw and the get in touch with ratio ea are identified 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 substantial sliding friction in the tooth get in touch with. If the sliding friction coefficient f = 0.1 – 0.3, it needs the transverse operating pressure position 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 ought to be compensated by the axial (or face) speak to ratio eb to ensure the total contact ratio eg = ea + eb ≥ 1.0. This can be achieved by using helical gears (Physique 4). Even so, helical gears apply the axial (thrust) induce on the gear bearings. The twice helical (or “herringbone”) gears (Body 4) allow to pay this force.
Large transverse pressure angles lead to increased bearing radial load that could be up to four to five occasions higher than for the traditional 20o pressure angle gears. Bearing collection and gearbox housing style ought to be done accordingly to hold this increased load without increased deflection.
Application of the asymmetric tooth for unidirectional drives permits improved efficiency. For the self-locking gears that are used to prevent backdriving, the same tooth flank is employed for both generating and locking modes. In this instance asymmetric tooth profiles give much higher transverse speak to ratio at the provided pressure angle compared to the symmetric tooth flanks. It makes it possible to lessen the helix angle and axial bearing load. For the self-locking gears which used to prevent inertial driving, distinct tooth flanks are used for traveling and locking modes. In this case, asymmetric tooth account with low-pressure angle provides high productivity for driving function and the contrary high-pressure angle tooth account is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype models were made predicated on the developed mathematical styles. The gear data are presented in the Desk 1, and the check gears are offered in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric electric motor was used to drive the actuator. A built-in rate and torque sensor was installed on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low rate shaft of the gearbox via coupling. The input and result torque and speed details had been captured in the data acquisition tool and further analyzed in a pc applying data analysis application. The instantaneous effectiveness of the actuator was calculated and plotted for a variety of speed/torque combination. Typical driving proficiency of the personal- locking equipment obtained during screening was above 85 percent. The self-locking home of the helical gear set in backdriving mode was likewise tested. In this test the external torque was applied to the output gear shaft and the angular transducer showed no angular movements of source shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been used in textile industry [2]. On the other hand, this type of gears has a large number of potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial traveling is not permissible. One of such app [7] of the self-locking gears for a continually variable valve lift system was advised for an motor vehicle engine.
Summary
In this paper, a principle of do the job of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and assessment of the apparatus prototypes has proved comparatively high driving efficiency and trusted self-locking. The self-locking gears may find many applications in a variety of industries. For example, in a control devices where position steadiness is very important (such as in auto, aerospace, medical, robotic, agricultural etc.) the self-locking allows to attain required performance. Like the worm self-locking gears, the parallel axis self-locking gears are very sensitive to operating circumstances. The locking dependability is influenced by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and needs comprehensive testing in all possible operating conditions.