Worm gearboxes with many combinations
Ever-Power offers a very wide selection of worm gearboxes. Because of the modular design the standard programme comprises many combinations in terms of selection of equipment housings, mounting and interconnection options, flanges, shaft patterns, kind of oil, surface remedies 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 homes in cast iron, light weight aluminum and stainless, worms in case hardened and polished steel and worm wheels in high-quality bronze of exceptional alloys ensuring the optimum wearability. The seals of the worm gearbox are provided with a dirt lip which effectively 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 enable reductions as high as 100:1 in one single step or 10.000:1 in a double lowering. An comparative gearing with the same equipment ratios and the same transferred electric power is bigger when compared to a worm gearing. In the mean time, the worm gearbox is normally in a far more simple design.
A double reduction may be composed of 2 typical gearboxes or as a special gearbox.
Compact design
Compact design is among the key terms of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished through the use of adapted gearboxes or unique gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very smooth operating of the worm equipment combined with the use of cast iron and great precision on part manufacturing and assembly. In connection with our precision gearboxes, we consider extra care and attention of any sound which can be interpreted as a murmur from the apparatus. Therefore the general noise degree 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 sometimes proves to be a decisive benefit producing the incorporation of the gearbox considerably simpler and smaller sized.The worm gearbox is an angle gear. This is often an advantage for incorporation into constructions.
Strong bearings in stable housing
The output shaft of the Ever-Power worm gearbox is very firmly embedded in the apparatus house and is perfect for direct suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger gear ratios, Ever-Power worm gearboxes will self locking gearbox provide a self-locking impact, which in lots of situations can be utilized as brake or as extra security. Also spindle gearboxes with a trapezoidal spindle are self-locking, making them perfect for a variety of solutions.
In most equipment drives, when generating torque is suddenly reduced as a result of electricity off, torsional vibration, vitality outage, or any mechanical inability at the transmission input part, then gears will be rotating either in the same path driven by the system inertia, or in the contrary route driven by the resistant output load because of gravity, springtime load, etc. The latter condition is known as backdriving. During inertial movement or backdriving, the driven output shaft (load) becomes the traveling one and the traveling input shaft (load) becomes the powered one. There are plenty of gear travel applications where result shaft driving is unwanted. As a way to prevent it, different types of brake or clutch equipment are used.
However, there are also solutions in the apparatus transmission that prevent inertial movement or backdriving using self-locking gears without any additional products. The most common one can be a worm gear with a minimal lead angle. In self-locking worm gears, torque used from the strain side (worm equipment) 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 swiftness, low gear mesh effectiveness, increased heat generation, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can make use of any gear ratio from 1:1 and larger. They have the generating mode and self-locking mode, when the inertial or backdriving torque is certainly applied to the output gear. At first these gears had very low ( <50 percent) driving performance that limited their application. Then it was proved [3] that substantial driving efficiency of these kinds of gears is possible. Criteria of the self-locking was analyzed in this post [4]. This paper explains the theory of the self-locking process for the parallel axis gears with symmetric and asymmetric tooth profile, and shows their suitability for unique 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. Practically all conventional equipment drives have the pitch point P situated in the active part the contact collection B1-B2 (Figure 1a and Physique 2a). This pitch point location provides low specific sliding velocities and friction, and, subsequently, high driving proficiency. In case when such gears are motivated by productivity load or inertia, they will be rotating freely, because the friction second (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, applied to the gear
T’1 – driven torque, applied to the pinion
F – driving force
F’ – traveling 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
To make gears self-locking, the pitch point P ought to be located off the dynamic portion the contact line B1-B2. There happen to be two options. Option 1: when the point P is placed between a centre of the pinion O1 and the idea B2, where the outer size of the gear intersects the contact series. 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 point P is placed between your point B1, where in fact the outer size of the pinion intersects the series contact and a centre of the gear O2. This type of gears can be self-locking with relatively high driving performance > 50 percent.
Another condition of self-locking is to have a enough 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 a lever of the power 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 end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot be fabricated with the expectations tooling with, for instance, the 20o pressure and rack. This makes them extremely suitable for Direct Gear Style® [5, 6] that provides required gear overall performance and from then on defines tooling parameters.
Direct Gear Design presents the symmetric equipment tooth created by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is shaped by two involutes of two unique base circles (Figure 3b). The tooth idea circle da allows preventing the pointed tooth hint. The equally spaced tooth form the apparatus. The fillet profile between teeth is designed independently to avoid interference and provide minimum bending anxiety. The functioning pressure angle aw and the contact 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 excessive sliding friction in the tooth contact. 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 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 ensure the total speak to ratio eg = ea + eb ≥ 1.0. This can be attained by applying helical gears (Shape 4). Nevertheless, helical gears apply the axial (thrust) power on the apparatus bearings. The twice helical (or “herringbone”) gears (Body 4) allow to compensate 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 conventional 20o pressure angle gears. Bearing collection and gearbox housing style should be done accordingly to carry this elevated load without excessive deflection.
Software of the asymmetric pearly whites for unidirectional drives allows for improved functionality. For the self-locking gears that are being used to prevent backdriving, the same tooth flank is utilized for both traveling and locking modes. In cases like this asymmetric tooth profiles give much higher transverse speak to ratio at the presented pressure angle compared to the symmetric tooth flanks. It makes it possible to lessen the helix position and axial bearing load. For the self-locking gears which used to prevent inertial driving, diverse tooth flanks are being used for driving and locking modes. In this instance, asymmetric tooth profile with low-pressure angle provides high performance for driving method and the opposite high-pressure angle tooth account is utilized for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype pieces were made predicated on the developed mathematical designs. The gear data are presented in the Table 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 motor was used to drive the actuator. An integrated velocity and torque sensor was installed on the high-swiftness shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low speed shaft of the gearbox via coupling. The type and productivity torque and speed facts were captured in the data acquisition tool and further analyzed in a computer applying data analysis program. The instantaneous productivity of the actuator was calculated and plotted for a wide variety of speed/torque combination. Average driving efficiency of the personal- locking gear obtained during screening was above 85 percent. The self-locking house of the helical gear set in backdriving mode was likewise tested. In this test the exterior torque was applied to the output equipment shaft and the angular transducer confirmed no angular motion of type shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been used in textile industry [2]. On the other hand, this type of gears has many potential applications in lifting mechanisms, assembly tooling, and other gear drives where in fact the backdriving or inertial driving is not permissible. Among such software [7] of the self-locking gears for a continually variable valve lift program was recommended for an car engine.
Summary
In this paper, a principle of job of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and examining of the gear prototypes has proved relatively high driving productivity and reputable self-locking. The self-locking gears may find many applications in various industries. For instance, in a control systems where position steadiness is essential (such as in automobile, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to accomplish required performance. Similar to the worm self-locking gears, the parallel axis self-locking gears are sensitive to operating conditions. The locking stability is affected by lubrication, vibration, misalignment, etc. Implementation of these gears should be finished with caution and requires comprehensive testing in all possible operating conditions.