Worm gearboxes with many combinations
Ever-Power offers an extremely wide variety of worm gearboxes. Because of the modular design the standard programme comprises many combinations when it comes to selection of gear housings, mounting and interconnection options, flanges, shaft patterns, 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 properties in cast iron, aluminium and stainless, worms in the event hardened and polished metal and worm wheels in high-quality bronze of exceptional alloys ensuring the the best wearability. The seals of the worm gearbox are given with a dirt lip which successfully resists dust and drinking water. In addition, the gearboxes are greased forever 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 single step or 10.000:1 in a double lowering. An equivalent gearing with the same equipment ratios and the same transferred ability is bigger when compared to a worm gearing. In the mean time, the worm gearbox is definitely in a far more simple design.
A double reduction could be composed of 2 standard 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 can be achieved 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 easy working of the worm gear combined with the utilization of cast iron and large precision on aspect manufacturing and assembly. Regarding the our precision gearboxes, we consider extra treatment of any sound which can be interpreted as a murmur from the apparatus. Therefore the general noise degree of our gearbox is normally 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 advantages making the incorporation of the gearbox significantly simpler and smaller sized.The worm gearbox can be an angle gear. This can often be an advantage for incorporation into constructions.
Strong bearings in sound housing
The output shaft of the Ever-Power worm gearbox is very firmly embedded in the apparatus house and is suitable for immediate suspension for wheels, movable arms and other parts rather than needing to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes provides a self-locking result, which in lots of situations can be utilized as brake or as extra reliability. Also spindle gearboxes with a trapezoidal spindle will be self-locking, making them suitable for a wide variety of solutions.
In most equipment drives, when traveling torque is suddenly reduced because of this of power off, torsional vibration, vitality outage, or any mechanical inability at the transmitting input side, then gears will be rotating either in the same direction driven by the system inertia, or in the contrary path driven by the resistant output load due to gravity, springtime load, etc. The latter state is called backdriving. During inertial action or backdriving, the powered output shaft (load) becomes the traveling one and the generating input shaft (load) turns into the driven one. There are various gear travel applications where result shaft driving is unwanted. So as to prevent it, different types of brake or clutch units are used.
However, there are also solutions in the gear transmission that prevent inertial motion or backdriving using self-locking gears without the additional equipment. The most frequent one is definitely a worm equipment with a minimal lead angle. In self-locking worm gears, torque applied from the load side (worm gear) is blocked, i.electronic. cannot drive the worm. Even so, their application includes some limitations: the crossed axis shafts’ arrangement, relatively high equipment ratio, low speed, low gear mesh performance, increased heat technology, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can use any equipment ratio from 1:1 and bigger. They have the driving mode and self-locking method, when the inertial or backdriving torque can be applied to the output gear. Primarily these gears had suprisingly low ( <50 percent) driving productivity that limited their application. Then it had been proved [3] that huge driving efficiency of this kind of gears is possible. Standards of the self-locking was analyzed in this article [4]. This paper explains the principle of the self-locking procedure for the parallel axis gears with symmetric and asymmetric tooth profile, and reveals their suitability for diverse applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents standard gears (a) and self-locking gears (b), in the event of inertial driving. Almost all conventional gear drives possess the pitch stage P situated in the active portion the contact brand B1-B2 (Figure 1a and Number 2a). This pitch stage location provides low specific sliding velocities and friction, and, therefore, high driving productivity. In case when this sort of gears are motivated by result load or inertia, they will be rotating freely, because the friction second (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’ – generating force, when the backdriving or 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 should be located off the lively portion the contact line B1-B2. There are two options. Alternative 1: when the point P is positioned between a middle of the pinion O1 and the point B2, where the outer size of the gear intersects the contact collection. 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 inserted between your point B1, where in fact the outer size of the pinion intersects the range contact and a centre of the gear O2. This sort of gears can be self-locking with relatively great driving effectiveness > 50 percent.
Another condition of self-locking is to have a adequate friction angle g to deflect the force F’ beyond the guts of the pinion O1. It creates the resisting self-locking point in time (torque) T’1 = F’ x L’1, where L’1 is definitely a lever of the drive F’1. This condition could be shown 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 position at the end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot become fabricated with the requirements tooling with, for instance, the 20o pressure and rack. This makes them incredibly suited to Direct Gear Style® [5, 6] that provides required gear performance and from then on defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth created by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is created by two involutes of two distinct base circles (Figure 3b). The tooth idea circle da allows preventing the pointed tooth suggestion. The equally spaced tooth form the apparatus. The fillet profile between teeth was created independently to avoid interference and offer minimum bending tension. The functioning pressure angle aw and the speak to ratio ea are described 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 self locking gearbox requires ruthless and excessive 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. Therefore, the transverse get in touch with ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse contact ratio ought to be compensated by the axial (or face) speak to ratio eb to guarantee the total speak to ratio eg = ea + eb ≥ 1.0. This can be attained by using helical gears (Number 4). Even so, helical gears apply the axial (thrust) power on the apparatus bearings. The dual helical (or “herringbone”) gears (Shape 4) allow to pay this force.
High transverse pressure angles cause increased bearing radial load that could be up to four to five times higher than for the conventional 20o pressure angle gears. Bearing assortment and gearbox housing style ought to be done accordingly to hold this increased load without extreme deflection.
App of the asymmetric tooth for unidirectional drives permits improved overall performance. For the self-locking gears that are being used to avoid backdriving, the same tooth flank is utilized for both traveling and locking modes. In this case asymmetric tooth profiles present much higher transverse speak to ratio at the granted pressure angle compared to the symmetric tooth flanks. It creates it possible to lessen the helix angle and axial bearing load. For the self-locking gears which used to prevent inertial driving, unique tooth flanks are used for generating and locking modes. In cases like this, asymmetric tooth account with low-pressure position provides high efficiency for driving function and the opposite high-pressure angle tooth account is employed for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype sets were made predicated on the developed mathematical products. The gear info are presented in the Desk 1, and the check gears are shown in Figure 5.
The schematic presentation of the test setup is demonstrated in Figure 6. The 0.5Nm electric electric motor was used to drive the actuator. A swiftness and torque sensor was installed on the high-swiftness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low acceleration shaft of the gearbox via coupling. The input and productivity torque and speed facts had been captured in the data acquisition tool and further analyzed in a computer employing data analysis software program. The instantaneous performance of the actuator was calculated and plotted for an array of speed/torque combination. Normal driving productivity of the personal- locking gear obtained during tests was above 85 percent. The self-locking home of the helical equipment occur backdriving mode was also tested. In this test the exterior torque was applied to the output equipment shaft and the angular transducer revealed no angular motion of source shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were used in textile industry [2]. However, this sort of gears has various potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial generating is not permissible. Among such application [7] of the self-locking gears for a continuously variable valve lift system was advised for an automobile engine.
Summary
In this paper, a basic principle of operate of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles happen to be shown, and testing of the gear prototypes has proved comparatively high driving efficiency and dependable self-locking. The self-locking gears could find many applications in a variety of industries. For example, in a control devices where position stableness is very important (such as for example in vehicle, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to attain required performance. Similar to the worm self-locking gears, the parallel axis self-locking gears are hypersensitive to operating circumstances. The locking dependability is damaged by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and requires comprehensive testing in all possible operating conditions.