Worm gearboxes with countless combinations
Ever-Power offers an extremely wide variety of worm gearboxes. Because of the modular design the standard programme comprises many combinations with regards to selection of equipment housings, mounting and connection options, flanges, shaft models, kind of oil, surface solutions 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 homes in cast iron, light weight aluminum and stainless, worms in case hardened and polished steel and worm tires in high-grade bronze of special alloys ensuring the ideal wearability. The seals of the worm gearbox are provided with a dust lip which efficiently resists dust and normal water. In addition, the gearboxes happen to be greased forever with synthetic oil.
Large reduction 100:1 in one 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 decrease. An comparative gearing with the same equipment ratios and the same transferred electrical power is bigger than a worm gearing. On the other hand, the worm gearbox is normally in a more simple design.
A double reduction could be composed of 2 typical gearboxes or as a special gearbox.
Compact design
Compact design is probably the key terms of the typical gearboxes of the Ever-Power-Series. Further optimisation can be achieved through the use of adapted gearboxes or unique gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is due to the very simple operating of the worm equipment combined with the application of cast iron and great precision on aspect manufacturing and assembly. Regarding the our accuracy gearboxes, we take extra attention of any sound which can be interpreted as a murmur from the apparatus. Therefore the general noise level of our gearbox is usually reduced to a complete 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 gain making 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 sound 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 parts rather than having to create a separate suspension.
Self locking
For larger gear ratios, Ever-Electricity worm gearboxes will provide a self-locking result, which in many situations can be utilised as brake or as extra reliability. Likewise spindle gearboxes with a trapezoidal spindle will be self-locking, making them suitable for a variety of solutions.
In most gear drives, when traveling torque is suddenly reduced therefore of electricity off, torsional vibration, electricity outage, or any mechanical failure at the transmission input area, then gears will be rotating either in the same route driven by the system inertia, or in the contrary direction driven by the resistant output load because of gravity, spring load, etc. The latter state is called backdriving. During inertial movement or backdriving, the powered output shaft (load) becomes the generating one and the generating input shaft (load) becomes the influenced one. There are lots of gear drive applications where output shaft self locking gearbox driving is undesirable. So as to prevent it, various kinds of brake or clutch devices are used.
However, there are also solutions in the gear transmitting that prevent inertial motion or backdriving using self-locking gears without the additional devices. The most frequent one is normally a worm gear with a low lead angle. In self-locking worm gears, torque applied from the strain side (worm equipment) is blocked, i.electronic. cannot travel the worm. Even so, their application includes some restrictions: the crossed axis shafts’ arrangement, relatively high equipment ratio, low speed, low gear mesh productivity, increased heat era, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can employ any equipment ratio from 1:1 and larger. They have the driving mode and self-locking function, when the inertial or backdriving torque is usually put on the output gear. Originally these gears had suprisingly low ( <50 percent) driving proficiency that limited their app. Then it had been proved [3] that large driving efficiency of this sort of gears is possible. Standards of the self-locking was analyzed in the following paragraphs [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 unique applications.
Self-Locking Condition
Physique 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents regular gears (a) and self-locking gears (b), in the event of inertial driving. Practically all conventional equipment drives possess the pitch level P located in the active part the contact range B1-B2 (Figure 1a and Body 2a). This pitch point location provides low particular sliding velocities and friction, and, because of this, high driving performance. In case when these kinds of gears are influenced by result load or inertia, they will be rotating freely, as the friction minute (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, put on the gear
T’1 – driven torque, put on the pinion
F – driving force
F’ – driving force, when the backdriving or perhaps 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 ought to be located off the active portion the contact line B1-B2. There are two options. Option 1: when the point P is positioned between a centre of the pinion O1 and the idea B2, where the outer size of the apparatus intersects the contact line. This makes the self-locking possible, but the driving efficiency will always be low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the idea P is located between the point B1, where in fact the outer size of the pinion intersects the collection contact and a centre of the gear O2. This type of gears can be self-locking with relatively huge driving efficiency > 50 percent.
Another condition of self-locking is to truly have a satisfactory friction angle g to deflect the force F’ beyond the center of the pinion O1. It generates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is a lever of the drive F’1. This condition can be provided 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 position at the tip of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot become fabricated with the expectations tooling with, for example, the 20o pressure and rack. This makes them extremely ideal for Direct Gear Design® [5, 6] that delivers required gear effectiveness 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 equipment tooth is shaped by two involutes of two several base circles (Figure 3b). The tooth tip circle da allows preventing the pointed tooth idea. The equally spaced pearly whites form the apparatus. The fillet profile between teeth is designed independently to avoid interference and provide minimum bending tension. The functioning 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 high sliding friction in the tooth contact. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure angle to aw = 75 – 85o. 
Consequently, the transverse speak to 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) contact ratio eb to guarantee the total speak to ratio eg = ea + eb ≥ 1.0. This can be achieved by applying helical gears (Number 4). However, helical gears apply the axial (thrust) push on the apparatus bearings. The twice helical (or “herringbone”) gears (Physique 4) allow to pay this force.
Huge transverse pressure angles lead to increased bearing radial load that may be up to four to five instances higher than for the traditional 20o pressure angle gears. Bearing selection and gearbox housing style should be done accordingly to hold this increased load without unnecessary deflection.
Software of the asymmetric pearly whites for unidirectional drives allows for improved functionality. 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 this instance asymmetric tooth profiles give much higher transverse speak to ratio at the granted pressure angle than the symmetric tooth flanks. It makes it possible to lessen the helix position and axial bearing load. For the self-locking gears that used to avoid inertial driving, numerous tooth flanks are used for generating and locking modes. In this instance, asymmetric tooth profile with low-pressure angle provides high performance for driving function and the opposite high-pressure angle tooth profile can be used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype units were made based on the developed mathematical types. The gear data are shown in the Table 1, and the check gears are offered in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric electric motor was used to operate a vehicle the actuator. A swiftness and torque sensor was installed on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low quickness shaft of the gearbox via coupling. The suggestions and end result torque and speed info were captured in the info acquisition tool and additional analyzed in a computer employing data analysis software. The instantaneous productivity 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 set in backdriving mode was as well tested. In this test the external torque was applied to the output gear shaft and the angular transducer revealed no angular movements of input 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 in fact the backdriving or inertial driving is not permissible. One of such software [7] of the self-locking gears for a consistently variable valve lift program was advised for an car engine.
Summary
In this paper, a basic principle of job 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 productivity and reputable self-locking. The self-locking gears could find many applications in a variety of industries. For example, in a control devices where position balance is important (such as for example in car, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to attain required performance. Like the worm self-locking gears, the parallel axis self-locking gears are hypersensitive to operating conditions. The locking stability 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.