self locking gearbox

Worm gearboxes with many combinations
Ever-Power offers a very wide variety of worm gearboxes. Due to the modular design the standard programme comprises countless combinations when it comes to selection of equipment housings, mounting and connection options, flanges, shaft styles, type of oil, surface therapies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is simple and well proven. We just use top quality components such as houses in cast iron, metal and stainless steel, worms in case hardened and polished metal and worm tires in high-quality bronze of self locking gearbox special alloys ensuring the ideal wearability. The seals of the worm gearbox are provided with a dirt lip which effectively resists dust and drinking water. Furthermore, the gearboxes are greased for life 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. Meanwhile, the worm gearbox is usually in a more simple design.
A double reduction could be composed of 2 normal gearboxes or as a particular gearbox.
Compact design
Compact design is among the key words of the standard gearboxes of the Ever-Power-Series. Further optimisation can be achieved through the use of adapted gearboxes or exceptional gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very soft working of the worm equipment combined with the use of cast iron and substantial precision on part manufacturing and assembly. In connection with our precision gearboxes, we have extra treatment of any sound that can be interpreted as a murmur from the apparatus. So the general noise degree of our gearbox is definitely 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 benefits producing the incorporation of the gearbox noticeably simpler and more compact.The worm gearbox can be an angle gear. This is often an advantage for incorporation into constructions.
Strong bearings in stable 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 having to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Power worm gearboxes will provide a self-locking result, which in many situations can be utilized as brake or as extra protection. Also spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them suitable for a broad range of solutions.
In most equipment drives, when driving torque is suddenly reduced because of this of electricity off, torsional vibration, ability outage, or any mechanical failing at the tranny input aspect, then gears will be rotating either in the same route driven by the machine inertia, or in the opposite route driven by the resistant output load due to gravity, early spring load, etc. The latter state is known as backdriving. During inertial action or backdriving, the influenced output shaft (load) becomes the generating one and the generating input shaft (load) becomes the driven one. There are plenty of gear drive applications where end result shaft driving is unwanted. In order to prevent it, different types of brake or clutch gadgets are used.
However, there are also solutions in the gear transmitting that prevent inertial movement or backdriving using self-locking gears without the additional products. The most frequent one is a worm equipment with a low lead angle. In self-locking worm gears, torque utilized from the load side (worm gear) is blocked, i.e. cannot drive the worm. Nevertheless, their application includes some constraints: the crossed axis shafts' arrangement, relatively high gear ratio, low velocity, low gear mesh effectiveness, increased heat era, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike
Self-Locking Condition
Body 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents typical gears (a) and self-locking gears (b), in the event of inertial driving. Pretty much all conventional gear drives possess the pitch stage P located in the active part the contact collection B1-B2 (Figure 1a and Physique 2a). This pitch point location provides low specific sliding velocities and friction, and, due to this fact, high driving proficiency. In case when this kind of gears are motivated by outcome load or inertia, they are 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, 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
In order to make gears self-locking, the pitch point P ought to be located off the lively portion the contact line B1-B2. There will be two options. Alternative 1: when the idea P is positioned between a center of the pinion O1 and the point B2, where in fact the outer size of the apparatus intersects the contact collection. This makes the self-locking possible, however the driving performance will always be low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the idea P is inserted between the point B1, where in fact the outer diameter of the pinion intersects the collection contact and a middle of the gear O2. This kind of gears can be self-locking with relatively high driving efficiency > 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 creates the resisting self-locking instant (torque) T'1 = F' x L'1, where L'1 is definitely a lever of the pressure 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 angle at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot become fabricated with the criteria tooling with, for instance, the 20o pressure and rack. This makes them extremely ideal for Direct Gear Design® [5, 6] that delivers required gear efficiency and from then on defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth formed by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is formed by two involutes of two several base circles (Figure 3b). The tooth suggestion circle da allows avoiding the pointed tooth suggestion. The equally spaced the teeth form the apparatus. The fillet profile between teeth is designed independently in order to avoid interference and provide minimum bending pressure. The operating pressure angle aw and the contact ratio ea are described 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).

Excessive transverse pressure angles bring about increased bearing radial load that may be up to four to five times higher than for the conventional 20o pressure angle gears. Bearing selection and gearbox housing style ought to be done accordingly to carry this elevated load without increased deflection.
App of the asymmetric pearly whites for unidirectional drives allows for improved efficiency. For the self-locking gears that are being used to prevent backdriving, the same tooth flank is used for both generating and locking modes. In this case asymmetric tooth profiles provide much higher transverse speak to 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, several tooth flanks are being used for generating and locking modes. In this case, asymmetric tooth account with low-pressure angle provides high efficiency for driving method 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 based on the developed mathematical types. The gear info are presented in the Table 1, and the check gears are presented in Figure 5.
The schematic presentation of the test setup is demonstrated in Figure 6. The 0.5Nm electric engine was used to drive the actuator. A built-in quickness and torque sensor was attached on the high-quickness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low acceleration shaft of the gearbox via coupling. The type and outcome torque and speed info had been captured in the info acquisition tool and additional analyzed in a pc using data analysis program. The instantaneous effectiveness of the actuator was calculated and plotted for a variety of speed/torque combination. Normal driving efficiency of the personal- locking equipment obtained during screening was above 85 percent. The self-locking real estate of the helical equipment set in backdriving mode was also tested. In this test the external torque was put on the output equipment shaft and the angular transducer showed no angular movement of suggestions shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were found in textile industry [2]. Nevertheless, this sort of gears has many potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial generating is not permissible. One of such request [7] of the self-locking gears for a constantly variable valve lift system was suggested for an automobile engine.
Summary
In this paper, a principle 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 screening of the gear prototypes has proved fairly high driving proficiency and efficient self-locking. The self-locking gears may find many applications in various industries. For example, in a control systems where position stableness is vital (such as for example in automotive, 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 sensitive to operating circumstances. The locking stability is affected by lubrication, vibration, misalignment, etc. Implementation of these gears should be finished with caution and needs comprehensive testing in all possible operating conditions.