self locking gearbox

Worm gearboxes with many combinations
Ever-Power offers an extremely wide variety of worm gearboxes. Due to the modular design the standard programme comprises countless combinations when it comes to selection of gear housings, mounting and connection options, flanges, shaft patterns, type of oil, surface therapies etc.
Sturdy and reliable
The look of the Ever-Power worm gearbox is easy and well proven. We only use high quality components such as homes in cast iron, aluminum and stainless, worms in the event hardened and polished metal and worm wheels in high-grade bronze of unique alloys ensuring the the best wearability. The seals of the worm gearbox are provided with a dust lip which efficiently resists dust and normal water. In addition, the gearboxes are greased for life with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes allow for reductions as high as 100:1 in one step or 10.000:1 in a double reduction. An comparative gearing with the same gear ratios and the same transferred power is bigger than a worm gearing. In the mean time, the worm gearbox is in a more simple design.
A double reduction may be composed of 2 common gearboxes or as a special gearbox.
Compact design
Compact design is probably the key terms of the typical gearboxes of the Ever-Power-Series. Further optimisation may be accomplished through the use of adapted gearboxes or distinctive gearboxes.
Low noise
Our worm gearboxes and actuators are extremely quiet. This is due to the very simple self locking gearbox working of the worm equipment combined with the utilization of cast iron and high precision on part manufacturing and assembly. Regarding the our precision gearboxes, we have extra care and attention of any sound that can be interpreted as a murmur from the apparatus. So the general noise degree of our gearbox can be reduced to a complete minimum.
Angle gearboxes
On the worm gearbox the input shaft and output shaft are perpendicular to one another. This often proves to be a decisive edge producing the incorporation of the gearbox considerably simpler and more compact.The worm gearbox can be an angle gear. This is normally 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 gear house and is ideal for immediate suspension for wheels, movable arms and other parts rather than having to create a separate suspension.
Self locking
For larger gear ratios, Ever-Electricity worm gearboxes provides a self-locking result, which in many situations works extremely well as brake or as extra security. Also spindle gearboxes with a trapezoidal spindle will be self-locking, making them suitable for a variety of solutions.
In most equipment drives, when generating torque is suddenly reduced because of this of power off, torsional vibration, electric power outage, or any mechanical inability at the tranny input aspect, then gears will be rotating either in the same way driven by the machine 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 motion or backdriving, the powered output shaft (load) turns into the generating one and the generating input shaft (load) becomes the motivated one. There are several gear drive applications where output shaft driving is unwanted. As a way to prevent it, different types of brake or clutch products are used.
However, there are also solutions in the apparatus tranny that prevent inertial movement or backdriving using self-locking gears with no additional equipment. The most typical one can be 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 travel the worm. On the other hand, their application includes some restrictions: the crossed axis shafts’ arrangement, relatively high gear ratio, low speed, low gear mesh productivity, increased heat era, etc.
Also, there happen to be parallel axis self-locking gears [1, 2]. These gears, unlike the worm gears, can make use of any equipment ratio from 1:1 and bigger. They have the driving mode and self-locking function, when the inertial or backdriving torque is certainly applied to the output gear. In the beginning these gears had suprisingly low ( <50 percent) driving effectiveness that limited their request. Then it was proved [3] that huge driving efficiency of this kind 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 method for the parallel axis gears with symmetric and asymmetric the teeth profile, and reveals their suitability for numerous applications.
Self-Locking Condition
Determine 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. Practically all conventional gear drives possess the pitch level P located in the active portion the contact range B1-B2 (Figure 1a and Body 2a). This pitch stage location provides low specific sliding velocities and friction, and, because of this, high driving proficiency. In case when such gears are powered by outcome load or inertia, they will be rotating freely, because the friction point in time (or torque) isn’t 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, put on the pinion
F – driving force
F’ – traveling force, when the backdriving or perhaps inertial torque applied to 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 dynamic portion the contact line B1-B2. There happen to be two options. Alternative 1: when the idea P is placed between a centre of the pinion O1 and the point B2, where the outer diameter of the apparatus intersects the contact collection. This makes the self-locking possible, but the driving proficiency will be low under 50 percent [3]. Choice 2 (figs 1b and 2b): when the point P is placed between your point B1, where in fact the outer diameter of the pinion intersects the range contact and a centre of the apparatus O2. This kind of gears could be self-locking with relatively great driving productivity > 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 instant (torque) T’1 = F’ x L’1, where L’1 is a lever of the power 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 quantity of teeth,
– involute profile position at the end of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are customized. They cannot end up being fabricated with the expectations tooling with, for instance, the 20o pressure and rack. This makes them incredibly ideal for Direct Gear Style® [5, 6] that provides required gear efficiency and from then on defines tooling parameters.
Direct Gear Style presents the symmetric gear tooth formed by two involutes of one base circle (Figure 3a). The asymmetric gear tooth is formed by two involutes of two distinct base circles (Figure 3b). The tooth tip circle da allows preventing the pointed tooth tip. The equally spaced the teeth form the apparatus. The fillet account between teeth is designed independently to avoid interference and provide minimum bending stress. The working pressure angle aw and the speak to 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 high pressure and large 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. Because of this, the transverse speak to ratio ea < 1.0 (typically 0.4 - 0.6). Lack of the transverse contact ratio should be compensated by the axial (or face) speak to ratio eb to guarantee the total speak to ratio eg = ea + eb ≥ 1.0. This could be achieved by employing helical gears (Determine 4). However, helical gears apply the axial (thrust) force on the apparatus bearings. The double helical (or “herringbone”) gears (Determine 4) allow to compensate this force.
Excessive transverse pressure angles lead to increased bearing radial load that may be up to four to five instances higher than for the traditional 20o pressure angle gears. Bearing variety and gearbox housing style ought to be done accordingly to hold this improved load without unnecessary deflection.
Program of the asymmetric pearly whites for unidirectional drives allows for improved performance. For the self-locking gears that are being used to avoid backdriving, the same tooth flank is utilized for both generating and locking modes. In cases like this asymmetric tooth profiles provide much higher transverse speak to ratio at the offered pressure angle compared to 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 prevent inertial driving, distinct tooth flanks are being used for driving and locking modes. In this case, asymmetric tooth account with low-pressure position provides high productivity for driving setting and the contrary high-pressure angle tooth profile is used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype units were made based on the developed mathematical styles. The gear data are shown 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 motor was used to drive the actuator. A swiftness and torque sensor was mounted on the high-acceleration shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low acceleration shaft of the gearbox via coupling. The input and result torque and speed facts were captured in the info acquisition tool and further analyzed in a pc applying data analysis program. The instantaneous productivity of the actuator was calculated and plotted for a broad range of speed/torque combination. Standard driving proficiency of the self- locking gear obtained during examining was above 85 percent. The self-locking real estate of the helical equipment set in backdriving mode was likewise tested. During this test the external torque was applied to the output equipment shaft and the angular transducer confirmed no angular movement of insight shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. On the other hand, this kind of gears has various potential applications in lifting mechanisms, assembly tooling, and other gear 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 recommended for an car engine.
In this paper, a theory of do the job of the self-locking gears has been described. Style specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and testing of the apparatus prototypes has proved fairly high driving proficiency and reputable self-locking. The self-locking gears could find many applications in a variety of industries. For example, in a control devices where position stableness is essential (such as 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 afflicted by lubrication, vibration, misalignment, etc. Implementation of the gears should be finished with caution and needs comprehensive testing in every possible operating conditions.


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