Worm gearboxes with many combinations
Ever-Power offers an extremely broad range of worm gearboxes. As a result of modular design the standard programme comprises countless combinations with regards to selection of equipment housings, mounting and interconnection options, flanges, shaft designs, kind of oil, surface remedies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is simple and well proven. We simply use top quality components such as houses in cast iron, aluminium and stainless steel, worms in the event hardened and polished metal and worm tires in high-quality bronze of distinctive alloys ensuring the the best wearability. The seals of the worm gearbox are provided with a dust lip which effectively resists dust and drinking water. In addition, the gearboxes will be greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes enable reductions of up to 100:1 in one step or 10.000:1 in a double reduction. An comparative gearing with the same equipment ratios and the same transferred electricity is bigger when compared to a worm gearing. In the meantime, the worm gearbox can be in a far more simple design.
A double reduction may be composed of 2 normal gearboxes or as a particular gearbox.
Compact design
Compact design is among the key words of the typical gearboxes of the Ever-Power-Series. Further optimisation can be achieved by using adapted gearboxes or distinctive gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is because 
of the very clean operating of the worm equipment combined with the use of cast iron and great precision on part manufacturing and assembly. Regarding the our accuracy gearboxes, we take extra health care of any sound that can be interpreted as a murmur from the gear. So the general noise level of our gearbox can be reduced to a complete minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to each other. This frequently proves to be a decisive benefits producing the incorporation of the gearbox considerably simpler and more compact.The worm gearbox can be an angle gear. This is often an advantage for incorporation into constructions.
Strong bearings in sturdy 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 areas rather than having to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Ability worm gearboxes will provide a self-locking impact, which in lots of situations can be utilised as brake or as extra reliability. Also 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 therefore of vitality off, torsional vibration, electrical power outage, or any mechanical inability at the transmitting input side, then gears will be rotating either in the same path driven by the machine inertia, or in the opposite course driven by the resistant output load because of gravity, spring load, etc. The latter condition is known as backdriving. During inertial action or backdriving, the motivated output shaft (load) turns into the generating one and the generating input shaft (load) becomes the influenced one. There are lots of gear travel applications where result shaft driving is undesirable. As a way to prevent it, different types of brake or clutch gadgets are used.
However, there are also solutions in the gear tranny that prevent inertial action or backdriving using self-locking gears without any additional gadgets. The most common one is definitely a worm equipment with a minimal lead angle. In self-locking worm gears, torque used from the load side (worm gear) is blocked, i.e. cannot travel the worm. On the other hand, their application includes some limitations: 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 the worm gears, can employ any gear ratio from 1:1 and larger. They have the generating mode and self-locking method, when the inertial or backdriving torque is usually applied to the output gear. At first these gears had very low ( <50 percent) traveling proficiency that limited their app. Then it was proved [3] that high driving efficiency of such gears is possible. Conditions 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 shows their suitability for distinct 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 the event of inertial driving. Almost all conventional gear drives possess the pitch point P situated in the active portion the contact range B1-B2 (Figure 1a and Figure 2a). This pitch point location provides low specific sliding velocities and friction, and, therefore, high driving effectiveness. In case when these kinds of gears are powered by end result load or inertia, they happen to be rotating freely, as the friction point in time (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, put on the gear
T’1 – driven torque, put on 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
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 point P is positioned between a middle of the pinion O1 and the point B2, where the outer diameter of the gear intersects the contact line. This makes the self-locking possible, but the driving effectiveness will end up being low under 50 percent [3]. Option 2 (figs 1b and 2b): when the point P is put between the point B1, where the outer diameter of the pinion intersects the series contact and a center of the apparatus O2. This sort of gears can be self-locking with relatively large driving productivity > 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 generates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is definitely a lever of the force F’1. This condition can 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 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 example, the 20o pressure and rack. This makes them extremely suitable for Direct Gear Style® [5, 6] that delivers required gear effectiveness and from then on defines tooling parameters.
Direct Gear Style presents the symmetric equipment tooth produced by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is created by two involutes of two numerous base circles (Figure 3b). The tooth hint circle da allows avoiding the self locking gearbox pointed tooth idea. The equally spaced teeth form the apparatus. The fillet profile between teeth was created independently in order to avoid interference and provide minimum bending tension. The operating pressure angle aw and the speak to 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).
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 angle to aw = 75 – 85o. As a result, the transverse get in touch with ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse get in touch with ratio ought to be compensated by the axial (or face) speak to ratio eb to ensure the total contact ratio eg = ea + eb ≥ 1.0. This is often achieved by employing helical gears (Shape 4). On the other hand, helical gears apply the axial (thrust) induce on the apparatus bearings. The dual helical (or “herringbone”) gears (Body 4) allow to compensate this force.
Great transverse pressure angles bring about increased bearing radial load that could be up to four to five occasions higher than for the traditional 20o pressure angle gears. Bearing selection and gearbox housing design ought to be done accordingly to hold this improved load without abnormal deflection.
Program of the asymmetric pearly whites for unidirectional drives permits 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 cases like this asymmetric tooth profiles provide much higher transverse contact ratio at the provided pressure angle than the symmetric tooth flanks. It creates it possible to lessen the helix angle and axial bearing load. For the self-locking gears that used to prevent inertial driving, several tooth flanks are being used for driving and locking modes. In this instance, asymmetric tooth account with low-pressure angle provides high performance for driving setting and the opposite high-pressure angle tooth account is employed for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype pieces were made based on the developed mathematical products. The gear info are provided in the Table 1, and the check gears are shown in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric electric motor was used to drive the actuator. A built-in velocity and torque sensor was installed on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low swiftness shaft of the gearbox via coupling. The source and result torque and speed facts had been captured in the data acquisition tool and further analyzed in a pc using data analysis computer software. The instantaneous performance of the actuator was calculated and plotted for a variety of speed/torque combination. Common driving performance of the personal- locking equipment obtained during evaluating was above 85 percent. The self-locking home of the helical equipment set in backdriving mode was as well tested. In this test the exterior torque was applied to the output gear shaft and the angular transducer revealed no angular movement of suggestions shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were found in textile industry [2]. Even so, this type of gears has a large number of potential applications in lifting mechanisms, assembly tooling, and other gear drives where the backdriving or inertial generating is not permissible. Among such software [7] of the self-locking gears for a constantly variable valve lift system was recommended for an vehicle 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 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 a variety of industries. For instance, in a control devices where position stability is essential (such as in automotive, aerospace, medical, robotic, agricultural etc.) the self-locking allows to attain required performance. Like the worm self-locking gears, the parallel axis self-locking gears are delicate to operating conditions. The locking reliability is afflicted by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and requires comprehensive testing in all possible operating conditions.