Worm gearboxes with many combinations
Ever-Power offers an extremely wide selection of worm gearboxes. Due to the modular design the standard programme comprises countless combinations in terms of selection of gear housings, mounting and connection options, flanges, shaft styles, 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 top quality components such as properties in cast iron, lightweight aluminum and stainless steel, worms in the event hardened and polished metal and worm wheels in high-quality bronze of exceptional alloys ensuring the ideal wearability. The seals of the worm gearbox are given with a dust lip which effectively resists dust and 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 reduction. An equivalent gearing with the same gear ratios and the same transferred power is bigger than a worm gearing. In the meantime, the worm gearbox can be in a more simple design.
A double reduction could be composed of 2 standard gearboxes or as a special gearbox.
Compact design
Compact design is probably the key words 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 easy working of the worm equipment combined with the usage of cast iron and great precision on component manufacturing and assembly. Regarding the our accuracy gearboxes, we consider extra care and attention of any sound that can be interpreted as a murmur from the gear. So the general noise level of our gearbox is certainly reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This typically proves to be a decisive benefits producing the incorporation of the gearbox substantially simpler and smaller sized.The worm gearbox is an angle gear. This is normally an advantage for incorporation into constructions.
Strong bearings in stable housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the apparatus house and is ideal for immediate suspension for wheels, movable arms and other areas rather than needing to create a separate suspension.
Self locking
For larger gear ratios, Ever-Electric power worm gearboxes will provide a self-locking impact, which in lots of situations can be utilised as brake or as extra security. Also spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them ideal for a variety of solutions.
In most gear drives, when traveling torque is suddenly reduced consequently of electrical power off, torsional vibration, ability outage, or any mechanical failure at the transmitting input aspect, then gears will be rotating either in the same path driven by the system inertia, or in the contrary path driven by the resistant output load due to gravity, early spring load, etc. The latter state is known as backdriving. During inertial movement or backdriving, the influenced output shaft (load) turns into the traveling one and the generating input shaft (load) turns into the powered one. There are lots of gear drive applications where productivity 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 apparatus tranny that prevent inertial action or backdriving using self-locking gears with no additional equipment. The most frequent one is certainly a worm equipment with a low lead angle. In self-locking worm gears, torque used from the strain side (worm equipment) is blocked, i.electronic. cannot drive the worm. Nevertheless, their application includes some constraints: the crossed axis shafts’ arrangement, relatively high equipment ratio, low acceleration, low gear mesh efficiency, 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 traveling mode and self-locking function, when the inertial or backdriving torque is usually applied to the output gear. In the beginning these gears had suprisingly low ( <50 percent) traveling effectiveness that limited their app. Then it was proved [3] that excessive driving efficiency of this kind 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 the teeth profile, and displays their suitability for unique applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents regular gears (a) and self-locking gears (b), in the event of inertial driving. Pretty much all conventional equipment drives have the pitch point P situated in the active portion the contact collection B1-B2 (Figure 1a and Shape 2a). This pitch point location provides low certain sliding velocities and friction, and, consequently, high driving performance. In case when this sort of gears are motivated by end result load or inertia, they will be rotating freely, as the friction minute (or torque) is not 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, applied to the gear
T’1 – driven torque, applied to the pinion
F – driving force
F’ – driving force, when the backdriving or 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 should be located off the active 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 in fact the outer diameter of the gear intersects the contact collection. This makes the self-locking possible, however the driving proficiency will always be low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the idea P is put between the point B1, where in fact the outer diameter of the pinion intersects the series contact and a middle of the apparatus O2. This sort of gears could be self-locking with relatively great driving efficiency > 50 percent.
Another condition of self-locking is to truly have a adequate friction angle g to deflect the force F’ beyond the center of the pinion O1. It generates the resisting self-locking minute (torque) T’1 = F’ x L’1, where L’1 is a lever of the induce F’1. This condition could be presented 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,
– self locking gearbox involute profile position at the end of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot become fabricated with the criteria tooling with, for instance, the 20o pressure and rack. This makes them extremely well suited for Direct Gear Style® [5, 6] that delivers required gear performance and from then on defines tooling parameters.
Direct Gear Style presents the symmetric equipment tooth formed by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is produced by two involutes of two distinct base circles (Figure 3b). The tooth suggestion circle da allows avoiding the pointed tooth idea. The equally spaced the teeth form the apparatus. The fillet profile between teeth is designed independently in order to avoid interference and offer minimum bending anxiety. 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 excessive sliding friction in the tooth get in touch with. If the sliding friction coefficient f = 0.1 – 0.3, it needs the transverse operating pressure angle to aw = 75 – 85o. As a result, the transverse contact 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 could be achieved by using helical gears (Determine 4). However, helical gears apply the axial (thrust) push on the apparatus bearings. The dual helical (or “herringbone”) gears (Physique 4) allow to pay this force.
High transverse pressure angles lead to increased bearing radial load that may be up to four to five times higher than for the conventional 20o pressure angle gears. Bearing variety and gearbox housing style should be done accordingly to carry this elevated load without extreme deflection.
App of the asymmetric the teeth for unidirectional drives allows for improved functionality. For the self-locking gears that are used to avoid backdriving, the same tooth flank is employed for both traveling 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 reduce the helix position and axial bearing load. For the self-locking gears which used to prevent inertial driving, several tooth flanks are being used for driving and locking modes. In cases like this, asymmetric tooth profile with low-pressure position provides high efficiency for driving method and the contrary high-pressure angle tooth account is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype models were made predicated on the developed mathematical types. The gear data are offered in the Table 1, and the test gears are shown 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. A built-in speed and torque sensor was mounted on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low rate shaft of the gearbox via coupling. The insight and productivity torque and speed information had been captured in the info acquisition tool and further analyzed in a computer employing data analysis software program. The instantaneous effectiveness of the actuator was calculated and plotted for an array of speed/torque combination. Normal driving effectiveness of the personal- locking equipment obtained during evaluating was above 85 percent. The self-locking home of the helical equipment occur backdriving mode was likewise tested. In this test the external torque was put on the output gear shaft and the angular transducer confirmed no angular motion of suggestions shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been used in textile industry [2]. Even so, this kind of gears has various potential applications in lifting mechanisms, assembly tooling, and other equipment drives where in fact the backdriving or inertial generating is not permissible. One of such program [7] of the self-locking gears for a continually variable valve lift program was advised for an automobile engine.
Summary
In this paper, a principle of do the 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 assessment of the gear prototypes has proved relatively high driving proficiency and trusted self-locking. The self-locking gears may find many applications in a variety of industries. For example, in a control devices where position balance is essential (such as for example in motor vehicle, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to accomplish required performance. Like the worm self-locking gears, the parallel axis self-locking gears are delicate to operating circumstances. The locking dependability is damaged by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and needs comprehensive testing in every possible operating conditions.