self locking gearbox

Worm gearboxes with countless combinations
Ever-Power offers a very wide range of worm gearboxes. Due to the modular design the typical programme comprises many combinations when it comes to selection of equipment housings, mounting and connection options, flanges, shaft models, type of oil, surface treatment options etc.
Sturdy and reliable
The look 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 special alloys ensuring the the best wearability. The seals of the worm gearbox are given with a dirt lip which properly resists dust and water. Furthermore, the gearboxes are 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 single step or 10.000:1 in a double decrease. An equivalent gearing with the same equipment ratios and the same transferred ability is bigger when compared to a worm gearing. In the meantime, the worm gearbox is certainly in a more simple design.
A double reduction may be composed of 2 common 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 because of the very easy jogging of the worm equipment combined with the use of cast iron and huge precision on aspect manufacturing and assembly. Regarding the our accuracy gearboxes, we take extra health care of any sound which can be interpreted as a murmur from the gear. So the general noise degree of our gearbox is usually 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 edge making the incorporation of the gearbox noticeably simpler and smaller sized.The worm gearbox can be an angle gear. This is normally an edge for incorporation into constructions.
Strong bearings in self locking gearbox stable housing
The output shaft of the Ever-Power worm gearbox is very firmly embedded in the apparatus house and is ideal for direct suspension for wheels, movable arms and other parts rather than having to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes will provide a self-locking impact, which in lots of situations works extremely well as brake or as extra security. 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 driving torque is suddenly reduced therefore of vitality off, torsional vibration, power outage, or any mechanical inability at the transmission input area, then gears will be rotating either in the same course driven by the machine inertia, or in the opposite course driven by the resistant output load because of gravity, planting season load, etc. The latter state is known as backdriving. During inertial action or backdriving, the powered output shaft (load) turns into the traveling one and the driving input shaft (load) turns into the influenced one. There are numerous gear travel applications where productivity shaft driving is undesirable. To be able to prevent it, several types of brake or clutch devices are used.
However, additionally, there are solutions in the apparatus transmission that prevent inertial movement or backdriving using self-locking gears with no additional devices. The most typical one is normally a worm equipment with a minimal lead angle. In self-locking worm gears, torque applied from the strain side (worm gear) is blocked, i.electronic. cannot drive the worm. However, their application includes some limitations: the crossed axis shafts’ arrangement, relatively high equipment ratio, low rate, low gear mesh effectiveness, increased heat era, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can utilize any equipment ratio from 1:1 and higher. They have the traveling mode and self-locking method, when the inertial or backdriving torque is normally applied to the output gear. In the beginning these gears had very low ( <50 percent) traveling performance that limited their app. Then it had been proved [3] that high driving efficiency of this kind of gears is possible. Requirements of the self-locking was analyzed in this post [4]. This paper explains the theory of the self-locking method for the parallel axis gears with symmetric and asymmetric pearly whites profile, and shows their suitability for unique applications.
Self-Locking Condition
Body 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 case of inertial driving. Virtually all conventional gear drives possess the pitch level P situated in the active part the contact line B1-B2 (Figure 1a and Determine 2a). This pitch stage location provides low specific sliding velocities and friction, and, consequently, high driving performance. In case when this kind of gears are driven by result load or inertia, they happen to be rotating freely, as 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, put on 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 should be located off the lively portion the contact line B1-B2. There are two options. Choice 1: when the point P is positioned between a middle of the pinion O1 and the idea B2, where in fact the outer size of the apparatus intersects the contact line. 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 point P is placed between your point B1, where in fact the outer diameter of the pinion intersects the range contact and a centre of the gear O2. This sort of gears can be self-locking with relatively substantial driving effectiveness > 50 percent.
Another condition of self-locking is to have a enough friction angle g to deflect the force F’ beyond the center of the pinion O1. It creates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is certainly a lever of the pressure 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 quantity of teeth,
– involute profile angle at the end of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot always be fabricated with the specifications tooling with, for example, the 20o pressure and rack. This makes them extremely ideal for Direct Gear Design® [5, 6] that delivers required gear functionality and after that defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth formed by two involutes of 1 base circle (Figure 3a). The asymmetric equipment tooth is formed by two involutes of two several base circles (Figure 3b). The tooth tip circle da allows preventing the pointed tooth tip. The equally spaced tooth form the apparatus. The fillet profile between teeth is designed independently to avoid interference and offer minimum bending anxiety. The operating pressure angle aw and the speak to 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 high 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. Due to this fact, 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) contact ratio eb to ensure the total speak to ratio eg = ea + eb ≥ 1.0. This can be achieved by using helical gears (Shape 4). On the other hand, helical gears apply the axial (thrust) drive on the apparatus bearings. The twice helical (or “herringbone”) gears (Physique 4) allow to compensate this force.
Substantial transverse pressure angles result in increased bearing radial load that may be up to four to five occasions higher than for the traditional 20o pressure angle gears. Bearing variety and gearbox housing style ought to be done accordingly to hold this improved load without extreme deflection.
Request of the asymmetric pearly whites for unidirectional drives permits improved effectiveness. For the self-locking gears that are being used to avoid backdriving, the same tooth flank is employed for both driving and locking modes. In cases like this asymmetric tooth profiles give much higher transverse get in touch with ratio at the provided 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 that used to avoid inertial driving, distinct tooth flanks are used for generating and locking modes. In cases like this, asymmetric tooth account with low-pressure position provides high proficiency for driving method and the opposite high-pressure angle tooth account is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype units were made based on the developed mathematical types. The gear info are presented in the Table 1, and the test gears are shown in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric motor was used to drive the actuator. A built-in speed and torque sensor was installed 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 source and output torque and speed facts were captured in the info acquisition tool and additional analyzed in a pc applying data analysis computer software. The instantaneous productivity of the actuator was calculated and plotted for a variety of speed/torque combination. Standard driving efficiency of the personal- locking gear obtained during assessment was above 85 percent. The self-locking home of the helical gear occur backdriving mode was as well tested. During this test the exterior torque was put on the output gear shaft and the angular transducer demonstrated no angular activity of input shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears had been used in textile industry [2]. On the other hand, this kind of gears has many potential applications in lifting mechanisms, assembly tooling, and other equipment drives where in fact the backdriving or inertial generating is not permissible. Among such software [7] of the self-locking gears for a consistently variable valve lift system was advised for an auto engine.
Summary
In this paper, a principle of operate of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and tests of the gear prototypes has proved fairly high driving proficiency and reliable self-locking. The self-locking gears could find many applications in various industries. For example, in a control devices where position steadiness is essential (such as in automotive, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to accomplish required performance. Like the worm self-locking gears, the parallel axis self-locking gears are very sensitive to operating conditions. The locking reliability is influenced by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and needs comprehensive testing in every possible operating conditions.