self locking gearbox

Worm gearboxes with countless combinations
Ever-Power offers an extremely wide range of worm gearboxes. self locking gearbox Because of the modular design the standard programme comprises countless combinations when it comes to selection of equipment housings, mounting and connection options, flanges, shaft models, type of oil, surface therapies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is easy and well proven. We simply use high quality components such as homes in cast iron, light weight aluminum and stainless, worms in the event hardened and polished steel and worm wheels in high-quality bronze of distinctive alloys ensuring the ideal wearability. The seals of the worm gearbox are provided with a dirt lip which effectively resists dust and normal water. In addition, the gearboxes are greased for life with synthetic oil.
Large reduction 100:1 in one step
As default the worm gearboxes allow for reductions of up to 100:1 in one single 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 when compared to a worm gearing. At the same time, the worm gearbox is definitely in a more simple design.
A double reduction could be composed of 2 regular gearboxes or as a particular gearbox.
Compact design
Compact design is probably the key terms of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or unique gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very clean operating of the worm gear combined with the application of cast iron and great precision on aspect manufacturing and assembly. In connection with our accuracy gearboxes, we take extra attention of any sound that can be interpreted as a murmur from the gear. Therefore the general noise level 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 typically proves to become a decisive benefits producing the incorporation of the gearbox noticeably simpler and smaller sized.The worm gearbox is an angle gear. This is normally 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 well suited 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-Electrical power worm gearboxes will provide a self-locking effect, which in lots of situations works extremely well as brake or as extra secureness. Likewise spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them perfect for an array of solutions.
In most gear drives, when driving torque is suddenly reduced because of this of electrical power off, torsional vibration, electricity outage, or any mechanical failing at the transmitting input aspect, then gears will be rotating either in the same direction driven by the machine inertia, or in the opposite route driven by the resistant output load because of gravity, early spring load, etc. The latter state is called backdriving. During inertial movement 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 result shaft driving is unwanted. To be able to prevent it, various kinds of brake or clutch products are used.
However, there are also solutions in the apparatus transmitting that prevent inertial action or backdriving using self-locking gears with no additional units. The most frequent one is usually a worm equipment with a low lead angle. In self-locking worm gears, torque applied from the load side (worm gear) is blocked, i.electronic. cannot travel the worm. However, their application comes with some restrictions: the crossed axis shafts’ arrangement, relatively high equipment ratio, low acceleration, low gear mesh efficiency, 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 gear ratio from 1:1 and larger. They have the driving mode and self-locking method, when the inertial or backdriving torque is normally put on the output gear. Originally these gears had very low ( <50 percent) generating productivity that limited their app. Then it was proved [3] that excessive driving efficiency of these kinds of gears is possible. Standards of the self-locking was analyzed in this posting [4]. This paper explains the principle of the self-locking method for the parallel axis gears with symmetric and asymmetric tooth profile, and displays their suitability for distinct applications.
Self-Locking Condition
Determine 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents typical gears (a) and self-locking gears (b), in case of inertial driving. Almost all conventional equipment drives have the pitch stage P situated in the active portion the contact series B1-B2 (Figure 1a and Number 2a). This pitch point location provides low particular sliding velocities and friction, and, because of this, high driving proficiency. In case when these kinds of gears are influenced by outcome load or inertia, they happen to be rotating freely, because the friction minute (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, applied to the pinion
F – driving force
F’ – traveling force, when the backdriving or 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 effective portion the contact line B1-B2. There happen to be two options. Option 1: when the idea 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 line. This makes the self-locking possible, but the driving performance will end up being low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the point P is positioned between the point B1, where the outer diameter of the pinion intersects the brand contact and a centre of the gear O2. This kind of gears could be self-locking with relatively huge driving efficiency > 50 percent.
Another condition of self-locking is to have a adequate friction angle g to deflect the force F’ beyond the center of the pinion O1. It generates the resisting self-locking point in time (torque) T’1 = F’ x L’1, where L’1 is certainly a lever of the push F’1. This condition can be presented as L’1min > 0 or
(1) Equation 1
or
(2) Equation 2
where:
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear number of teeth,
– involute profile angle at the tip of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot become fabricated with the benchmarks tooling with, for instance, the 20o pressure and rack. This makes them extremely suited to Direct Gear Style® [5, 6] that provides required gear functionality and after that defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth shaped 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 tip circle da allows preventing the pointed tooth suggestion. The equally spaced the teeth form the apparatus. The fillet account between teeth was created independently to avoid interference and provide minimum bending anxiety. The working pressure angle aw and the speak to ratio ea are defined 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 great sliding friction in the tooth get in touch with. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure position to aw = 75 – 85o. As a result, the transverse speak to ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse contact ratio should be compensated by the axial (or face) contact ratio eb to guarantee the total contact ratio eg = ea + eb ≥ 1.0. This can be achieved by employing helical gears (Determine 4). However, helical gears apply the axial (thrust) power on the gear bearings. The dual helical (or “herringbone”) gears (Determine 4) allow to pay this force.
Large transverse pressure angles cause increased bearing radial load that may be up to four to five instances higher than for the conventional 20o pressure angle gears. Bearing variety and gearbox housing design should be done accordingly to carry this elevated load without abnormal deflection.
Software of the asymmetric teeth for unidirectional drives allows for improved functionality. For the self-locking gears that are being used to prevent backdriving, the same tooth flank can be used for both driving and locking modes. In this instance asymmetric tooth profiles provide much higher transverse get in touch with ratio at the presented pressure angle than the symmetric tooth flanks. It makes it possible to reduce the helix position and axial bearing load. For the self-locking gears which used to avoid inertial driving, several tooth flanks are being used for generating and locking modes. In cases like this, asymmetric tooth profile with low-pressure angle provides high performance for driving method and the contrary high-pressure angle tooth profile can be used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype pieces were made based on the developed mathematical products. 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 engine was used to operate a vehicle the actuator. A built-in rate and torque sensor was mounted on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low acceleration shaft of the gearbox via coupling. The insight and end result torque and speed data had been captured in the info acquisition tool and further analyzed in a pc using data analysis program. The instantaneous productivity of the actuator was calculated and plotted for a wide selection of speed/torque combination. Standard driving productivity of the personal- locking equipment obtained during testing was above 85 percent. The self-locking home of the helical equipment set in backdriving mode was also tested. In this test the external torque was applied to the output equipment shaft and the angular transducer demonstrated no angular movements of insight shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. On the other hand, this kind of gears has various potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial generating is not permissible. One of such software [7] of the self-locking gears for a continuously variable valve lift system was recommended for an car engine.
Summary
In this paper, a principle of function 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 gear prototypes has proved fairly high driving productivity and reliable self-locking. The self-locking gears may find many applications in various industries. For example, in a control devices where position steadiness is important (such as for example in automotive, 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 delicate to operating circumstances. The locking dependability is damaged by lubrication, vibration, misalignment, etc. Implementation of the gears should be done with caution and needs comprehensive testing in all possible operating conditions.

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