Worm gearboxes with countless combinations
Ever-Power offers an extremely wide range of worm gearboxes. Because of the modular design the typical programme comprises many combinations with regards to selection of gear housings, mounting and interconnection options, flanges, shaft models, type of oil, surface solutions etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is simple and well proven. We only use high quality components such as residences in cast iron, light weight aluminum and stainless steel, worms in case hardened and polished steel and worm tires in high-grade bronze of specialized alloys ensuring the optimum wearability. The seals of the worm gearbox are given with a dirt lip which efficiently resists dust and drinking water. In addition, the gearboxes happen to be greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes enable 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 electricity is bigger than a worm gearing. In the meantime, the worm gearbox is certainly 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 phrases of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or specialized gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very smooth jogging of the worm equipment combined with the utilization of cast iron and large precision on aspect 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 gear. Therefore the general noise level 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 one another. This often proves to become a decisive edge producing the incorporation of the gearbox substantially simpler and more compact.The worm gearbox is an angle gear. This is normally an edge for incorporation into constructions.
Strong bearings in stable housing
The output shaft of the Ever-Power worm gearbox is very firmly embedded in the gear house and is well suited for immediate suspension for wheels, movable arms and other areas rather than having to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes provides a self-locking impact, which in many situations can be utilised as brake or as extra security. Also spindle gearboxes with a trapezoidal spindle are self-locking, making them ideal for a broad range of solutions.
In most equipment drives, when generating torque is suddenly reduced consequently of self locking gearbox ability off, torsional vibration, ability outage, or any mechanical inability at the transmission input side, then gears will be rotating either in the same route driven by the system inertia, or in the contrary way driven by the resistant output load due to gravity, planting season load, etc. The latter state is known as backdriving. During inertial action or backdriving, the driven output shaft (load) becomes the traveling one and the generating input shaft (load) becomes the influenced one. There are various gear drive applications where end result shaft driving is unwanted. In order to prevent it, several types of brake or clutch devices are used.
However, additionally, there are solutions in the apparatus tranny that prevent inertial action or backdriving using self-locking gears without any additional units. The most typical one is usually a worm equipment with a low lead angle. In self-locking worm gears, torque used from the load side (worm gear) is blocked, i.electronic. cannot travel the worm. However, their application includes some restrictions: the crossed axis shafts’ arrangement, relatively high equipment ratio, low speed, low gear mesh proficiency, increased heat era, etc.
Also, there will be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can utilize any equipment ratio from 1:1 and larger. They have the generating mode and self-locking function, when the inertial or backdriving torque is usually applied to the output gear. In the beginning these gears had very low ( <50 percent) traveling proficiency that limited their application. Then it was proved [3] that great driving efficiency of such gears is possible. Criteria of the self-locking was analyzed in this post [4]. This paper explains the theory of the self-locking procedure for the parallel axis gears with symmetric and asymmetric tooth profile, and reveals their suitability for different applications.
Self-Locking Condition
Body 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents standard gears (a) and self-locking gears (b), in case of inertial driving. Pretty much all conventional gear drives have the pitch stage P situated in the active portion the contact range B1-B2 (Figure 1a and Body 2a). This pitch level location provides low particular sliding velocities and friction, and, therefore, high driving proficiency. In case when this kind of gears are influenced by result load or inertia, they happen to be rotating freely, because the friction minute (or torque) is not 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, put on the pinion
F – driving force
F’ – traveling 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 ought to be located off the productive portion the contact line B1-B2. There happen to be two options. Option 1: when the idea P is positioned between a centre of the pinion O1 and the idea B2, where the outer diameter of the apparatus intersects the contact brand. This makes the self-locking possible, but the driving productivity will always be low under 50 percent [3]. Option 2 (figs 1b and 2b): when the idea P is put between the point B1, where the outer diameter of the pinion intersects the range contact and a center of the gear O2. This kind of gears could be self-locking with relatively substantial driving effectiveness > 50 percent.
Another condition of self-locking is to truly have a enough friction angle g to deflect the force F’ beyond the center 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 induce F’1. This condition could 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 amount of teeth,
– involute profile position at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot end up being fabricated with the criteria tooling with, for example, the 20o pressure and rack. This makes them very well suited for 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 1 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 tip. The equally spaced pearly whites 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 contact ratio ea are defined 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).
Conditions (1) and (2) show that self-locking requires high pressure and huge sliding friction in the tooth contact. If the sliding friction coefficient f = 0.1 – 0.3, it needs the transverse operating pressure position to aw = 75 – 85o. Consequently, the transverse get in touch with ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse speak to ratio ought to be compensated by the axial (or face) speak to ratio eb to ensure the total speak to ratio eg = ea + eb ≥ 1.0. This is often achieved by applying helical gears (Figure 4). On the other hand, helical gears apply the axial (thrust) push on the apparatus bearings. The twice helical (or “herringbone”) gears (Shape 4) allow to pay this force.
High transverse pressure angles bring about increased bearing radial load that could be up to four to five circumstances higher than for the traditional 20o pressure angle gears. Bearing variety and gearbox housing design ought to be done accordingly to carry this elevated load without excessive deflection.
Request of the asymmetric pearly whites for unidirectional drives permits improved overall performance. For the self-locking gears that are being used to prevent backdriving, the same tooth flank can be used for both generating and locking modes. In this instance asymmetric tooth profiles present much higher transverse get in touch with ratio at the offered pressure angle than the symmetric tooth flanks. It creates it possible to lessen the helix position and axial bearing load. For the self-locking gears that used to avoid inertial driving, distinct tooth flanks are being used for driving and locking modes. In this instance, asymmetric tooth profile with low-pressure position provides high productivity for driving method and the opposite high-pressure angle tooth profile can be used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype models were made based on the developed mathematical designs. The gear info are presented in the Desk 1, and the test gears are offered in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric motor was used to drive the actuator. An integrated speed and torque sensor was attached on the high-swiftness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low rate shaft of the gearbox via coupling. The type and outcome torque and speed facts were captured in the data acquisition tool and additional analyzed in a computer employing data analysis application. The instantaneous effectiveness of the actuator was calculated and plotted for a variety of speed/torque combination. Standard driving effectiveness of the personal- locking gear obtained during screening was above 85 percent. The self-locking house of the helical equipment set in backdriving mode was as well tested. In this test the external torque was put on the output equipment shaft and the angular transducer showed no angular movements of input shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears had been used in textile industry [2]. Even so, this type of gears has various potential applications in lifting mechanisms, assembly tooling, and other gear drives where the backdriving or inertial generating is not permissible. One of such app [7] of the self-locking gears for a constantly variable valve lift system was recommended for an motor vehicle 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 testing of the apparatus prototypes has proved fairly high driving performance and dependable self-locking. The self-locking gears could find many applications in a variety of industries. For instance, in a control devices where position stability is essential (such as in automobile, 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 sensitive to operating circumstances. The locking reliability is affected by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and requires comprehensive testing in all possible operating conditions.
