self locking gearbox

Worm gearboxes with many combinations
Ever-Power offers a very wide range 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 procedures etc.
Sturdy and reliable
The design of the Ever-Power worm gearbox is simple and well proven. We only use top quality components such as homes in cast iron, aluminum and stainless, worms in the event hardened and polished steel and worm wheels in high-grade bronze of unique alloys ensuring the optimum wearability. The seals of the worm gearbox are provided with a dirt lip which effectively resists dust and water. Furthermore, the gearboxes happen to be greased for life 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 decrease. An comparative gearing with the same gear ratios and the same transferred electric power is bigger than a worm gearing. Meanwhile, the worm gearbox is in a more simple design.
A double reduction may be composed of 2 normal gearboxes or as a special gearbox.
Compact design
Compact design is among the key phrases of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or unique gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is because of the very even operating of the worm equipment combined with the use of cast iron and huge precision on element manufacturing and assembly. Regarding the our accuracy gearboxes, we take extra care and attention of any sound which can be interpreted as a murmur from the gear. So the general noise level of our gearbox can be reduced to an absolute minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to each other. This frequently proves to become a decisive benefit making the incorporation of the gearbox substantially simpler and more compact.The worm gearbox is an angle gear. This is often an edge for incorporation into constructions.
Strong bearings in sturdy housing
The output shaft of the Ever-Power worm gearbox is quite firmly embedded in the apparatus house and is well suited for direct suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Ability worm gearboxes will provide a self-locking impact, which in many situations can be utilised as brake or as extra secureness. As well spindle gearboxes with a trapezoidal spindle are self-locking, making them perfect for a variety of solutions.
In most gear drives, when driving torque is suddenly reduced as a result of ability off, torsional vibration, electricity outage, or any mechanical failing at the tranny input aspect, then gears will be rotating either in the same course driven by the system inertia, or in the opposite route driven by the resistant output load due to gravity, spring load, etc. The latter condition is known as backdriving. During inertial movement or backdriving, the influenced output shaft (load) becomes the driving one and the traveling input shaft (load) becomes the influenced one. There are many gear travel applications where self locking gearbox productivity shaft driving is undesirable. In order to prevent it, several types of brake or clutch gadgets are used.
However, additionally, there are solutions in the apparatus transmitting that prevent inertial action or backdriving using self-locking gears with no additional products. The most typical one is a worm gear 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 comes with some constraints: the crossed axis shafts’ arrangement, relatively high equipment ratio, low acceleration, low gear mesh efficiency, 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 function, when the inertial or backdriving torque is usually put on the output gear. At first these gears had very low ( <50 percent) generating performance that limited their app. Then it was proved [3] that excessive driving efficiency of such gears is possible. Conditions of the self-locking was analyzed on this page [4]. This paper explains the theory of the self-locking process for the parallel axis gears with symmetric and asymmetric pearly whites profile, and displays their suitability for unique applications.
Self-Locking Condition
Determine 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents conventional gears (a) and self-locking gears (b), in case of inertial driving. Pretty much all conventional equipment drives have the pitch point P located in the active part the contact series B1-B2 (Figure 1a and Determine 2a). This pitch point location provides low certain sliding velocities and friction, and, consequently, high driving effectiveness. In case when this kind of gears are powered by productivity load or inertia, they are rotating freely, because the friction moment (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, 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 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 happen to be two options. Choice 1: when the idea P is positioned between a center of the pinion O1 and the idea B2, where in fact the outer diameter of the apparatus intersects the contact brand. This makes the self-locking possible, but the driving efficiency will always be low under 50 percent [3]. Option 2 (figs 1b and 2b): when the idea P is located between the point B1, where the outer size of the pinion intersects the line contact and a middle of the gear O2. This kind of gears could be self-locking with relatively substantial driving proficiency > 50 percent.
Another condition of self-locking is to have a ample friction angle g to deflect the force F’ beyond the center of the pinion O1. It creates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is a lever of the push F’1. This condition can be offered as L’1min > 0 or
(1) Equation 1
(2) Equation 2
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear amount of teeth,
– involute profile angle at the tip of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot be fabricated with the benchmarks tooling with, for example, the 20o pressure and rack. This makes them extremely suitable for Direct Gear Design® [5, 6] that delivers required gear functionality and from then on defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth formed by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is produced by two involutes of two different base circles (Figure 3b). The tooth tip circle da allows avoiding the pointed tooth hint. The equally spaced pearly whites form the gear. The fillet profile between teeth is designed independently in order to avoid interference and provide minimum bending stress. The working pressure angle aw and the get in touch with 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
inv(x) = tan x – x – involute function of the profile angle x (in radians).
Conditions (1) and (2) show that self-locking requires high pressure and large 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. Consequently, the transverse contact ratio ea < 1.0 (typically 0.4 - 0.6). Insufficient the transverse speak to ratio should be compensated by the axial (or face) get in touch with ratio eb to ensure the total get in touch with ratio eg = ea + eb ≥ 1.0. This could be achieved by employing helical gears (Determine 4). Nevertheless, helical gears apply the axial (thrust) pressure on the gear bearings. The double helical (or “herringbone”) gears (Physique 4) allow to compensate this force.
Great transverse pressure angles lead to increased bearing radial load that may be up to four to five situations higher than for the traditional 20o pressure angle gears. Bearing collection and gearbox housing design should be done accordingly to carry this elevated load without high deflection.
Software of the asymmetric pearly whites for unidirectional drives permits improved effectiveness. For the self-locking gears that are used to avoid backdriving, the same tooth flank is employed for both driving and locking modes. In cases like this asymmetric tooth profiles give much higher transverse get in touch with ratio at the offered 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 avoid inertial driving, diverse tooth flanks are used for traveling and locking modes. In this instance, asymmetric tooth profile with low-pressure angle provides high productivity for driving setting and the contrary high-pressure angle tooth account can be used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical gear prototype models were made predicated on the developed mathematical designs. The gear info are provided in the Table 1, and the test gears are presented in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric engine was used to operate a vehicle the actuator. An integrated rate and torque sensor was mounted on the high-rate shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was connected to the low velocity shaft of the gearbox via coupling. The type and end result torque and speed details were captured in the info acquisition tool and additional analyzed in a computer applying data analysis program. The instantaneous efficiency of the actuator was calculated and plotted for a wide range of speed/torque combination. Typical driving effectiveness of the personal- locking equipment obtained during testing was above 85 percent. The self-locking property of the helical gear set in backdriving mode was as well tested. During this test the exterior torque was put on the output gear shaft and the angular transducer showed no angular activity of suggestions shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. Even so, this kind 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 app [7] of the self-locking gears for a continually variable valve lift program was recommended for an automotive engine.
In this paper, a theory of function 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 fairly high driving productivity 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 balance is important (such as in auto, aerospace, medical, robotic, agricultural etc.) the self-locking allows to accomplish required performance. Like the worm self-locking gears, the parallel axis self-locking gears are delicate to operating circumstances. The locking reliability is afflicted by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and requires comprehensive testing in every possible operating conditions.