Worm gearboxes with countless combinations
Ever-Power offers a very broad range of worm gearboxes. Because of the modular design the standard programme comprises many combinations in terms of selection of equipment housings, mounting and connection options, flanges, shaft patterns, kind of oil, surface therapies 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 houses in cast iron, light weight aluminum and stainless steel, worms in case hardened and polished metal and worm wheels in high-quality bronze of distinctive alloys ensuring the the best possible wearability. The seals of the worm gearbox are provided with a dirt lip which efficiently resists dust and water. In addition, the gearboxes will be greased for life 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 decrease. An comparative gearing with the same equipment ratios and the same transferred electricity is bigger than a worm gearing. In the mean time, the worm gearbox is in a more simple design.
A double reduction could be composed of 2 normal 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 by using adapted gearboxes or specialized gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very clean jogging of the worm equipment combined with the use of cast iron and high precision on component manufacturing and assembly. Regarding the our precision gearboxes, we have extra attention of any sound that can be interpreted as a murmur from the gear. Therefore the general noise level of our gearbox is usually reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to each other. This generally proves to be a decisive advantage producing the incorporation of the gearbox significantly simpler and more compact.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 direct suspension for wheels, movable arms and other parts rather than having to create a separate suspension.
Self locking
For larger gear ratios, Ever-Electrical power worm gearboxes provides a self-locking effect, which in lots of situations works extremely well as brake or as extra secureness. As well spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them ideal for a variety of solutions.
In most equipment drives, when generating torque is suddenly reduced as a result of vitality off, torsional vibration, electric power outage, or any mechanical inability at the transmission input aspect, then gears will be rotating either in the same route driven by the machine inertia, or in the contrary path driven by the resistant output load due to gravity, springtime load, etc. The latter condition is known as backdriving. During inertial motion or backdriving, the driven output shaft (load) becomes the generating one and the driving input shaft (load) turns into the powered one. There are several gear drive applications where result shaft driving is unwanted. In order to prevent it, several types of brake or clutch gadgets are used.
However, there are also solutions in the gear transmitting that prevent inertial motion or backdriving using self-locking gears without any additional gadgets. The most frequent one is usually a worm gear with a low lead angle. In self-locking worm gears, torque utilized from the load side (worm equipment) is blocked, i.electronic. cannot drive the worm. However, their application comes with some limitations: the crossed axis shafts’ arrangement, relatively high gear ratio, low swiftness, low gear mesh efficiency, increased heat era, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can make use of any equipment ratio from 1:1 and higher. They have the traveling mode and self-locking method, when the inertial or backdriving torque is certainly put on the output gear. Originally these gears had very low ( <50 percent) traveling proficiency that limited their app. Then it had been proved [3] that substantial driving efficiency of such gears is possible. Standards of the self-locking was analyzed in this posting [4]. This paper explains the theory of the self-locking method for the parallel axis gears with symmetric and asymmetric pearly whites profile, and shows their suitability for numerous applications.
Self-Locking Condition
Number 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. Almost all conventional gear drives have the pitch stage P located in the active portion the contact collection B1-B2 (Figure 1a and Number 2a). This pitch level location provides low certain sliding velocities and friction, and, therefore, high driving efficiency. In case when this kind of gears are driven by productivity load or inertia, they will be rotating freely, as the friction point in time (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, put on 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
In order to make gears self-locking, the pitch point P ought to be located off the dynamic portion the contact line B1-B2. There are two options. Alternative 1: when the point P is positioned between a center of the pinion O1 and the idea B2, where the outer size of the apparatus intersects the contact series. This makes the self-locking possible, however the driving productivity will be low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the idea P is placed between the point B1, where the outer size of the pinion intersects the brand contact and a centre of the gear O2. This type of gears could be self-locking with relatively excessive driving efficiency > 50 percent.
Another condition of self-locking is to have a satisfactory friction angle g to deflect the force F’ beyond the guts of the pinion O1. It self locking gearbox creates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is usually a lever of the induce F’1. This condition could 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 amount of teeth,
– involute profile position at the end of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot end up being fabricated with the criteria tooling with, for instance, the 20o pressure and rack. This makes them incredibly well suited for Direct Gear Style® [5, 6] that provides required gear functionality and after that defines tooling parameters.
Direct Gear Design presents the symmetric equipment tooth shaped by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is shaped by two involutes of two numerous base circles (Figure 3b). The tooth tip circle da allows preventing the pointed tooth hint. The equally spaced the teeth form the apparatus. The fillet profile between teeth is designed independently to avoid interference and provide minimum bending tension. The operating pressure angle aw and the get in touch with ratio ea are identified 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 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 position to aw = 75 – 85o. Because of this, the transverse contact ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse get in touch with ratio should be compensated by the axial (or face) get in touch with ratio eb to ensure the total speak to ratio eg = ea + eb ≥ 1.0. This can be achieved by applying helical gears (Body 4). On the other hand, helical gears apply the axial (thrust) pressure on the gear bearings. The double helical (or “herringbone”) gears (Determine 4) allow to pay this force.
Great transverse pressure angles bring about increased bearing radial load that could be up to four to five times higher than for the conventional 20o pressure angle gears. Bearing selection and gearbox housing design ought to be done accordingly to carry this elevated load without abnormal deflection.
Request of the asymmetric the teeth for unidirectional drives permits improved performance. For the self-locking gears that are used to avoid backdriving, the same tooth flank is utilized for both generating and locking modes. In this instance asymmetric tooth profiles offer much higher transverse contact ratio at the granted pressure angle than the symmetric tooth flanks. It makes it possible to reduce the helix angle and axial bearing load. For the self-locking gears that used to prevent inertial driving, different tooth flanks are being used for traveling and locking modes. In this case, 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 gear prototype sets were made based on the developed mathematical styles. The gear data are offered in the Desk 1, and the test gears are shown in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric engine was used to operate a vehicle the actuator. A built-in velocity and torque sensor was installed on the high-acceleration shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low speed shaft of the gearbox via coupling. The source and end result torque and speed data were captured in the info acquisition tool and additional analyzed in a pc applying data analysis software program. The instantaneous effectiveness of the actuator was calculated and plotted for an array of speed/torque combination. Common driving performance of the self- locking gear obtained during screening was above 85 percent. The self-locking real estate of the helical gear occur backdriving mode was also tested. During this test the external torque was applied to the output equipment shaft and the angular transducer showed no angular activity of suggestions shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were found in textile industry [2]. However, this type of gears has a large number of potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial traveling is not permissible. One of such request [7] of the self-locking gears for a constantly variable valve lift program was advised for an automobile engine.
Summary
In this paper, a principle of function of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and examining of the gear prototypes has proved fairly high driving effectiveness and trusted self-locking. The self-locking gears could find many applications in various industries. For example, in a control devices where position steadiness is vital (such as for example in auto, 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 hypersensitive to operating conditions. The locking reliability is damaged by lubrication, vibration, misalignment, etc. Implementation of the gears should be done with caution and needs comprehensive testing in every possible operating conditions.