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self locking gearbox

Worm gearboxes with many combinations
Ever-Power offers an extremely wide variety of worm gearboxes. As a result of modular design the typical programme comprises many combinations with regards to selection of gear housings, mounting and connection options, flanges, shaft patterns, type of oil, surface remedies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is simple and well proven. We simply use high quality components such as residences in cast iron, metal and stainless, worms in the event hardened and polished steel and worm tires in high-quality bronze of unique alloys ensuring the maximum wearability. The seals of the worm gearbox are provided with a dust lip which effectively 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 allow for reductions as high as 100:1 in one single step or 10.000:1 in a double lowering. An equivalent gearing with the same equipment ratios and the same transferred power is bigger than a worm gearing. In the mean time, the worm gearbox is usually in a far more simple design.
A double reduction could be composed of 2 typical gearboxes or as a particular gearbox.
Compact design
Compact design is probably the key terms of the standard gearboxes of the Ever-Power-Series. Further optimisation may be accomplished by using adapted gearboxes or distinctive gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is because of the very even jogging of the worm equipment combined with the usage of cast iron and great precision on element manufacturing and assembly. In connection with our accuracy gearboxes, we have extra care of any sound which can be interpreted as a murmur from the apparatus. So the general noise level of our gearbox is normally reduced to a complete minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This generally proves to become a decisive edge producing the incorporation of the gearbox noticeably simpler and smaller sized.The worm gearbox can be an angle gear. This is normally an edge for incorporation into constructions.
Strong bearings in solid housing
The output shaft of the Ever-Power worm gearbox is quite 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-Electric power worm gearboxes will provide a self-locking impact, which in lots of situations can be utilised as brake or as extra protection. Likewise spindle gearboxes with a trapezoidal spindle will be self-locking, making them suitable for an array of solutions.
In most gear drives, when traveling torque is suddenly reduced therefore of electrical power off, torsional vibration, ability outage, or any mechanical failing at the tranny input area, then gears will be rotating either in the same direction driven by the system inertia, or in the opposite path 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 driving one and the driving input shaft (load) becomes the motivated one. There are plenty of gear travel applications where result shaft driving is undesirable. In order to prevent it, various kinds of brake or clutch devices are used.
However, there are also solutions in the gear tranny that prevent inertial action or backdriving using self-locking gears without any additional units. The most frequent one is usually a worm equipment with a minimal lead angle. In self-locking worm gears, torque applied from the strain side (worm gear) is blocked, i.electronic. cannot travel the worm. Nevertheless, their application includes some limitations: the crossed axis shafts’ arrangement, relatively high gear ratio, low rate, low gear mesh effectiveness, increased heat technology, 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 larger. They have the generating mode and self-locking mode, when the inertial or backdriving torque is usually put on the output gear. In the beginning these gears had suprisingly low ( <50 percent) driving efficiency that limited their program. Then it had been proved [3] that large driving efficiency of these kinds of gears is possible. Conditions of the self-locking was analyzed in this posting [4]. This paper explains the basic principle of the self-locking process for the parallel axis gears with symmetric and asymmetric tooth profile, and displays their suitability for distinct applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in the event of backdriving. Figure 2 presents conventional gears (a) and self-locking gears (b), in case of inertial driving. Almost all conventional gear drives have the pitch stage P located in the active part the contact collection B1-B2 (Figure 1a and Body 2a). This pitch point location provides low certain sliding velocities and friction, and, subsequently, high driving effectiveness. In case when this kind of gears are influenced by 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’ – 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 ought to be located off the lively portion the contact line B1-B2. There happen to be two options. Option 1: when the idea P is placed between a middle of the pinion O1 and the point B2, where in fact the outer diameter of the apparatus intersects the contact range. This makes the self-locking possible, however the driving proficiency will always be low under 50 percent [3]. Option 2 (figs 1b and 2b): when the point P is located between your point B1, where in fact the outer size of the pinion intersects the range 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 have a sufficient friction angle g to deflect the force F’ beyond the guts of the pinion O1. It generates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 can be a lever of the power F’1. This condition can be offered as L’1min > 0 or
(1) self locking gearbox Equation 1
or
(2) Equation 2
where:
u = n2/n1 – equipment ratio,
n1 and n2 – pinion and gear amount of teeth,
– involute profile angle at the tip of the apparatus tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot end up being fabricated with the specifications tooling with, for instance, the 20o pressure and rack. This makes them extremely suitable for Direct Gear Design® [5, 6] that delivers required gear efficiency and from then on defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth shaped by two involutes of 1 base circle (Figure 3a). The asymmetric equipment tooth is shaped by two involutes of two distinct base circles (Figure 3b). The to
oth suggestion circle da allows preventing the pointed tooth tip. The equally spaced tooth form the apparatus. The fillet profile between teeth was created independently to avoid interference and offer minimum bending pressure. The working pressure angle aw and the get in touch with ratio ea are described 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 large sliding friction in the tooth speak to. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure angle to aw = 75 – 85o. As a result, 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) contact ratio eb to guarantee the total speak to ratio eg = ea + eb ≥ 1.0. This is often attained by using helical gears (Body 4). However, helical gears apply the axial (thrust) push on the apparatus bearings. The double helical (or “herringbone”) gears (Body 4) allow to pay this force.
Huge transverse pressure angles cause increased bearing radial load that may 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 hold this elevated load without high deflection.
Request of the asymmetric the teeth for unidirectional drives allows for improved functionality. For the self-locking gears that are used to prevent backdriving, the same tooth flank is employed for both generating and locking modes. In this case asymmetric tooth profiles present much higher transverse speak to ratio at the given pressure angle than the symmetric tooth flanks. It creates it possible to lessen the helix position and axial bearing load. For the self-locking gears that used to avoid inertial driving, distinct tooth flanks are being used for generating and locking modes. In this instance, asymmetric tooth account with low-pressure position provides high productivity for driving mode and the contrary 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 Table 1, and the check gears are shown in Figure 5.
The schematic presentation of the test setup is displayed in Figure 6. The 0.5Nm electric engine was used to drive the actuator. A swiftness and torque sensor was attached on the high-velocity shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low quickness shaft of the gearbox via coupling. The insight and outcome torque and speed details were captured in the info acquisition tool and further analyzed in a computer using data analysis software program. The instantaneous proficiency of the actuator was calculated and plotted for an array of speed/torque combination. Standard driving performance 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 likewise tested. In this test the exterior torque was applied to the output gear shaft and the angular transducer showed no angular motion of input shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears were found in textile industry [2]. Even so, this type of gears has various potential applications in lifting mechanisms, assembly tooling, and other equipment drives where the backdriving or inertial generating is not permissible. Among such application [7] of the self-locking gears for a consistently variable valve lift system was advised for an motor vehicle engine.
Summary
In this paper, a theory of do the job of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and tests of the gear prototypes has proved comparatively high driving effectiveness and reputable self-locking. The self-locking gears could find many applications in various industries. For instance, in a control systems where position balance is vital (such as in car, aerospace, medical, robotic, agricultural etc.) the self-locking will allow to achieve required performance. Like the worm self-locking gears, the parallel axis self-locking gears are very sensitive to operating conditions. The locking dependability is afflicted by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and requires comprehensive testing in all possible operating conditions.

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