Worm gearboxes with countless combinations
Ever-Power offers a very wide variety of worm gearboxes. Because of the modular design the typical programme comprises many combinations when it comes to selection of gear housings, mounting and connection options, flanges, shaft styles, type of oil, surface procedures 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 properties in cast iron, aluminium and stainless steel, worms in case hardened and polished steel and worm tires in high-quality bronze of specialized alloys ensuring the the best wearability. The seals of the worm gearbox are provided with a dust lip which successfully resists dust and water. In addition, the gearboxes will be greased for life 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 step or 10.000:1 in a double decrease. An comparative gearing with the same equipment ratios and the same transferred electric power is bigger when compared to a worm gearing. At the same time, the worm gearbox is certainly 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 one of the key terms of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or exceptional gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very even running of the worm gear combined with the utilization of cast iron and excessive precision on aspect manufacturing and assembly. In connection with our precision gearboxes, we have extra health care of any sound that can be interpreted as a murmur from the apparatus. Therefore the general noise level of our gearbox is normally 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 edge making the incorporation of the gearbox substantially simpler and more compact.The worm gearbox can be an angle gear. This is often 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 perfect for immediate suspension for wheels, movable arms and other parts rather than needing to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes provides a self-locking impact, which in many situations works extremely well as brake or as extra reliability. Likewise spindle gearboxes with a trapezoidal spindle will 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 ability off, torsional vibration, power outage, or any mechanical failing at the transmission input part, then gears will be rotating either in the same course driven by the system inertia, or in the opposite path driven by the resistant output load because of gravity, early spring load, etc. The latter condition is called backdriving. During inertial action or backdriving, the driven output shaft (load) turns into the driving one and the traveling input shaft (load) turns into the influenced one. There are lots of gear drive applications where outcome shaft driving is undesirable. So that you can prevent it, different types of brake or clutch equipment are used.
However, additionally, there are solutions in the gear tranny that prevent inertial motion or backdriving using self-locking gears without the 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 load side (worm gear) is blocked, i.electronic. cannot drive the worm. On the other hand, their application includes some constraints: the crossed axis shafts’ arrangement, relatively high equipment ratio, low speed, low gear mesh productivity, increased heat generation, 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 higher. They have the generating mode and self-locking function, when the inertial or backdriving torque is normally applied to the output gear. Primarily these gears had suprisingly low ( <50 percent) traveling effectiveness that limited their app. Then it was proved [3] that substantial driving efficiency of these kinds of gears is possible. Requirements of the self-locking was analyzed on this page [4]. This paper explains the theory of the self-locking procedure for the parallel axis gears with symmetric and asymmetric teeth profile, and reveals their suitability for unique applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. self locking gearbox Figure 2 presents typical gears (a) and self-locking gears (b), in case of inertial driving. Almost all conventional gear drives have the pitch point P situated in the active part the contact brand B1-B2 (Figure 1a and Determine 2a). This pitch point location provides low particular sliding velocities and friction, and, therefore, high driving performance. In case when such gears are powered by outcome load or inertia, they are rotating freely, as the friction second (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’ – generating 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 ought to be located off the lively portion the contact line B1-B2. There will be two options. Choice 1: when the idea P is placed between a center of the pinion O1 and the idea B2, where the outer size of the apparatus intersects the contact collection. This makes the self-locking possible, however the driving proficiency will become low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the idea P is positioned between the point B1, where in fact the outer diameter of the pinion intersects the brand contact and a middle of the gear O2. This kind of gears could be self-locking with relatively high driving productivity > 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 creates the resisting self-locking point in time (torque) T’1 = F’ x L’1, where L’1 is a lever of the induce F’1. This condition can be presented 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 gear tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot always be fabricated with the requirements tooling with, for instance, the 20o pressure and rack. This makes them extremely suited to Direct Gear Style® [5, 6] that delivers required gear efficiency and after that defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth shaped by two involutes of 1 base circle (Figure 3a). The asymmetric equipment tooth is formed by two involutes of two distinct base circles (Figure 3b). The tooth suggestion circle da allows avoiding the pointed tooth suggestion. The equally spaced pearly whites form the apparatus. The fillet profile between teeth was created independently in order to avoid interference and offer minimum bending tension. The operating pressure angle aw and the get in touch with 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 ruthless and huge 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. Therefore, 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) contact ratio eb to guarantee the total speak to ratio eg = ea + eb ≥ 1.0. This could be achieved by applying helical gears (Shape 4). Nevertheless, helical gears apply the axial (thrust) drive on the gear bearings. The twice helical (or “herringbone”) gears (Figure 4) allow to pay this force.
High transverse pressure angles lead to increased bearing radial load that could be up to four to five moments higher than for the conventional 20o pressure angle gears. Bearing variety and gearbox housing design ought to be done accordingly to carry this improved load without high deflection.
Software of the asymmetric tooth for unidirectional drives permits improved functionality. For the self-locking gears that are being used to prevent backdriving, the same tooth flank is used for both generating and locking modes. In cases like this asymmetric tooth profiles offer much higher transverse get in touch with ratio at the granted pressure angle than the symmetric tooth flanks. It creates it possible to reduce the helix angle and axial bearing load. For the self-locking gears that used to prevent inertial driving, distinct tooth flanks are used for driving and locking modes. In this instance, asymmetric tooth account with low-pressure angle provides high effectiveness for driving function and the opposite high-pressure angle tooth profile is utilized for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype units were made predicated on the developed mathematical styles. The gear info are offered in the Desk 1, and the check gears are offered in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric electric motor was used to drive the actuator. A velocity and torque sensor was mounted 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 output torque and speed data were captured in the data acquisition tool and additional analyzed in a computer applying data analysis software program. The instantaneous productivity of the actuator was calculated and plotted for an array of speed/torque combination. Average driving productivity of the personal- locking gear obtained during evaluating was above 85 percent. The self-locking property of the helical equipment occur backdriving mode was as well tested. In this test the external torque was put on the output gear shaft and the angular transducer confirmed no angular movement of type shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears were used in textile industry [2]. However, this sort 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 software [7] of the self-locking gears for a constantly variable valve lift system was recommended for an auto engine.
Summary
In this paper, a theory of operate of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles will be shown, and testing of the apparatus prototypes has proved relatively high driving proficiency and reputable self-locking. The self-locking gears could find many applications in various industries. For instance, in a control devices where position steadiness is very important (such as for example in car, aerospace, medical, robotic, agricultural etc.) the self-locking allows to achieve required performance. Like the worm self-locking gears, the parallel axis self-locking gears are sensitive to operating conditions. The locking stability is influenced by lubrication, vibration, misalignment, etc. Implementation of the gears should be done with caution and needs comprehensive testing in all possible operating conditions.