self locking gearbox

Worm gearboxes with many combinations
Ever-Power offers a very wide variety of worm gearboxes. As a result of modular design the standard programme comprises countless combinations in terms of selection of equipment housings, mounting and connection options, flanges, shaft models, type of oil, surface treatments 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 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 particular alloys ensuring the the best possible wearability. The seals of the worm gearbox are given with a dust lip which successfully resists dust and water. Furthermore, the gearboxes happen to be greased for life with synthetic oil.
Large reduction 100:1 in one step
As default the worm gearboxes enable reductions of up to 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 vitality is bigger when compared to a worm gearing. In the mean time, the worm gearbox is normally in a more simple design.
A double reduction may be composed of 2 standard gearboxes or as a particular gearbox.
Compact design
Compact design is probably the key phrases of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or particular gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is due to the very clean operating of the worm equipment combined with the application of cast iron and huge precision on part manufacturing and assembly. In connection with our precision gearboxes, we take extra care of any sound which can be interpreted as a murmur from the apparatus. So the general noise degree 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 become a decisive edge making the incorporation of the gearbox noticeably simpler and more compact.The worm gearbox is an angle gear. This can often be 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 ideal for immediate suspension for wheels, movable arms and other areas rather than needing to build a separate suspension.
Self locking
For larger equipment ratios, Ever-Electrical power worm gearboxes provides a self-locking effect, which in many situations can be used as brake or as extra protection. As well spindle gearboxes with a trapezoidal spindle happen to be self-locking, making them ideal for a wide range of solutions.
In most gear drives, when generating torque is suddenly reduced because of this of electrical power off, torsional vibration, electrical power outage, or any mechanical inability at the transmission input part, then gears will be rotating either in the same way driven by the system inertia, or in the contrary route driven by the resistant output load because of gravity, planting season load, etc. The latter state is called backdriving. During inertial action or backdriving, the influenced output shaft (load) becomes the generating one and the generating input shaft (load) becomes the influenced one. There are lots of gear travel applications where result shaft driving is unwanted. To be able to prevent it, various kinds of brake or clutch units are used.
However, additionally, there are solutions in the gear transmitting that prevent inertial action or backdriving using self-locking gears without any additional products. The most frequent one is normally a worm equipment with a minimal lead angle. In self-locking worm gears, torque applied from the load side (worm equipment) is blocked, i.e. cannot travel the worm. However, their application includes some constraints: the crossed axis shafts’ arrangement, relatively high gear ratio, low quickness, low gear mesh proficiency, increased heat technology, etc.
Also, there are parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can utilize any equipment ratio from 1:1 and higher. They have the traveling mode and self-locking function, when the inertial or backdriving torque is definitely put on the output gear. Originally these gears had very low ( <50 percent) traveling performance that limited their app. Then it was proved [3] that great driving efficiency of this kind of gears is possible. Conditions of the self-locking was analyzed in this post [4]. This paper explains the theory of the self-locking method for the parallel axis gears with symmetric and asymmetric pearly whites profile, and displays their suitability for diverse 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. Almost all conventional equipment drives possess the pitch stage P located in the active part the contact line B1-B2 (Figure 1a and Determine 2a). This pitch point location provides low specific sliding velocities and friction, and, therefore, high driving efficiency. In case when these kinds of gears are powered by result load or inertia, they are rotating freely, because the friction instant (or torque) is not 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, put on the gear
T’1 – driven torque, applied to the pinion
F – driving force
F’ – driving 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
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 centre of the pinion O1 and the point B2, where the outer diameter of the gear intersects the contact range. This makes the self-locking possible, but the driving proficiency will be low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the idea P is located between your point B1, where the outer diameter of the pinion intersects the series contact and a centre of the apparatus O2. This type of gears can be self-locking with relatively excessive driving proficiency > 50 percent.
Another condition of self-locking is to have a satisfactory 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 usually a lever of the push F’1. This condition could be offered as L’1min > 0 or
(1) Equation 1
(2) Equation 2
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear number of teeth,
– involute profile angle at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot be fabricated with the specifications tooling with, for example, the 20o pressure and rack. This makes them extremely ideal for Direct Gear Style® [5, 6] that provides required gear performance and from then on defines tooling parameters.
Direct Gear Design presents the symmetric gear tooth produced by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is shaped by two involutes of two numerous base circles (Figure 3b). The tooth suggestion circle da allows preventing the pointed tooth suggestion. The equally self locking gearbox spaced teeth form the apparatus. The fillet profile between teeth was created independently in order to avoid interference and provide minimum bending tension. The operating pressure angle aw and the contact 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
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 substantial sliding friction in the tooth speak to. If the sliding friction coefficient f = 0.1 – 0.3, it needs the transverse operating pressure angle to aw = 75 – 85o. Therefore, 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 contact ratio eg = ea + eb ≥ 1.0. This could be achieved by applying helical gears (Physique 4). Even so, helical gears apply the axial (thrust) induce on the apparatus bearings. The twice helical (or “herringbone”) gears (Figure 4) allow to compensate this force.
High transverse pressure angles bring about 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 increased load without abnormal deflection.
Program of the asymmetric the teeth for unidirectional drives permits improved effectiveness. For the self-locking gears that are being used to prevent backdriving, the same tooth flank is utilized for both driving and locking modes. In this case asymmetric tooth profiles give much higher transverse speak to ratio at the given pressure angle compared to 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 avoid inertial driving, distinct tooth flanks are used for generating and locking modes. In this case, asymmetric tooth profile with low-pressure position provides high effectiveness for driving method and the opposite high-pressure angle tooth account is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype pieces were made predicated on the developed mathematical models. The gear info are presented in the Desk 1, and the test gears are presented in Figure 5.
The schematic presentation of the test setup is shown in Figure 6. The 0.5Nm electric engine was used to operate a vehicle the actuator. A built-in speed and torque sensor was mounted on the high-velocity shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low swiftness shaft of the gearbox via coupling. The insight and result torque and speed facts were captured in the data acquisition tool and additional analyzed in a computer employing data analysis program. The instantaneous proficiency of the actuator was calculated and plotted for a broad range of speed/torque combination. Standard driving productivity of the personal- locking equipment obtained during screening was above 85 percent. The self-locking real estate of the helical equipment set in backdriving mode was as well tested. In this test the exterior torque was applied to the output equipment shaft and the angular transducer demonstrated no angular motion of source shaft, which verified the self-locking condition.
Potential Applications
Initially, self-locking gears were found in textile industry [2]. Even so, this type of gears has many potential applications in lifting mechanisms, assembly tooling, and other equipment drives where in fact the backdriving or inertial generating is not permissible. Among such software [7] of the self-locking gears for a constantly variable valve lift program was suggested for an vehicle engine.
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 are shown, and evaluating of the apparatus prototypes has proved comparatively high driving efficiency and reliable self-locking. The self-locking gears could find many applications in various industries. For example, in a control devices where position balance is vital (such as for example in automotive, 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 sensitive to operating circumstances. The locking reliability is afflicted by lubrication, vibration, misalignment, etc. Implementation of these gears should be done with caution and needs comprehensive testing in every possible operating conditions.