Worm gearboxes with many combinations
Ever-Power offers an extremely wide selection of worm gearboxes. As a result of modular design the standard programme comprises many combinations in terms of selection of equipment housings, mounting and interconnection options, flanges, shaft styles, type of oil, surface solutions 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, metal and stainless, worms in the event hardened and polished metal and worm tires in high-quality bronze of unique alloys ensuring the ideal wearability. The seals of the worm gearbox are provided with a dust lip which efficiently resists dust and water. Furthermore, the gearboxes will be greased forever with synthetic oil.
Large reduction 100:1 in a single step
As default the worm gearboxes allow for reductions of up to 100:1 in one single step or 10.000:1 in a double lowering. An comparative gearing with the same equipment ratios and the same transferred vitality is bigger when compared to a worm gearing. In the meantime, the worm gearbox is normally in a far more simple design.
A double reduction may be composed of 2 normal gearboxes or as a special gearbox.
Compact design
Compact design is one of the key phrases of the typical gearboxes of the Ever-Power-Series. Further optimisation can be achieved through the use of adapted gearboxes or special gearboxes.
Low noise
Our worm gearboxes and actuators are really quiet. This is due to the very clean jogging of the worm gear combined with the use of cast iron and excessive precision on aspect 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 is certainly reduced to a complete 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 benefits making the incorporation of the gearbox considerably simpler and smaller sized.The worm gearbox can be an angle gear. This is often an advantage 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 well suited for immediate suspension for wheels, movable arms and other areas rather than needing to create a separate suspension.
Self locking
For larger equipment ratios, Ever-Power worm gearboxes provides a self-locking impact, which in lots of situations works extremely well as brake or as extra reliability. Likewise spindle gearboxes with a trapezoidal spindle are self-locking, making them well suited for a variety of solutions.
In most gear drives, when generating torque is suddenly reduced because of this of power off, torsional vibration, vitality outage, or any mechanical failing at the transmitting input side, then gears will be rotating either in the same course driven by the machine inertia, or in the contrary way 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 generating one and the driving input shaft (load) turns into the influenced one. There are various gear travel applications where productivity shaft driving is undesirable. In order to prevent it, different types of brake or self locking gearbox clutch products are used.
However, there are also solutions in the apparatus transmitting that prevent inertial action or backdriving using self-locking gears without any additional products. The most typical one is normally 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 travel the worm. On the other hand, their application comes with some limitations: the crossed axis shafts’ arrangement, relatively high gear ratio, low speed, low gear mesh efficiency, increased heat technology, 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 bigger. They have the traveling mode and self-locking method, when the inertial or backdriving torque is applied to the output gear. Originally these gears had very low ( <50 percent) generating performance that limited their software. Then it was proved [3] that huge driving efficiency of this kind of gears is possible. Criteria of the self-locking was analyzed in this posting [4]. This paper explains the principle of the self-locking procedure for the parallel axis gears with symmetric and asymmetric teeth profile, and shows their suitability for numerous applications.
Self-Locking Condition
Number 1 presents conventional gears (a) and self-locking gears (b), in case of backdriving. Figure 2 presents regular gears (a) and self-locking gears (b), in the event of inertial driving. Practically all conventional equipment drives have the pitch level P situated in the active portion the contact line B1-B2 (Figure 1a and Figure 2a). This pitch level location provides low specific sliding velocities and friction, and, consequently, high driving productivity. In case when such gears are motivated by outcome load or inertia, they will be rotating freely, as the friction point in time (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’ – driving 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 should be located off the effective portion the contact line B1-B2. There happen to be two options. Alternative 1: when the idea P is placed between a middle of the pinion O1 and the point B2, where the outer diameter of the gear intersects the contact line. This makes the self-locking possible, but the driving productivity will always be low under 50 percent [3]. Alternative 2 (figs 1b and 2b): when the point P is positioned between the point B1, where the outer size of the pinion intersects the line contact and a centre of the apparatus O2. This type of gears can be self-locking with relatively excessive driving effectiveness > 50 percent.
Another condition of self-locking is to have a enough friction angle g to deflect the force F’ beyond the guts of the pinion O1. It creates the resisting self-locking second (torque) T’1 = F’ x L’1, where L’1 is usually a lever of the induce F’1. This condition can be provided 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 angle at the tip of the gear tooth.
Design of Self-Locking Gears
Self-locking gears are custom. They cannot end up being fabricated with the requirements tooling with, for example, the 20o pressure and rack. This makes them very suited to Direct Gear Style® [5, 6] that provides required gear efficiency and from then on defines tooling parameters.
Direct Gear Style presents the symmetric equipment tooth produced by two involutes of one base circle (Figure 3a). The asymmetric equipment tooth is produced by two involutes of two unique base circles (Figure 3b). The tooth hint circle da allows avoiding the pointed tooth tip. The equally spaced pearly whites form the apparatus. The fillet profile between teeth was created independently in order to avoid interference and provide minimum bending pressure. The working pressure angle aw and the speak to ratio ea are identified 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
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 contact. If the sliding friction coefficient f = 0.1 – 0.3, it requires the transverse operating pressure angle to aw = 75 – 85o. Consequently, the transverse contact ratio ea < 1.0 (typically 0.4 - 0.6). Insufficient the transverse get in touch with ratio ought to be compensated by the axial (or face) get in touch with ratio eb to guarantee the total contact ratio eg = ea + eb ≥ 1.0. This can be attained by applying helical gears (Number 4). Even so, helical gears apply the axial (thrust) power on the apparatus bearings. The twice helical (or “herringbone”) gears (Shape 4) allow to compensate this force.
Great transverse pressure angles result in increased bearing radial load that could be up to four to five situations higher than for the traditional 20o pressure angle gears. Bearing selection and gearbox housing style should be done accordingly to carry this increased load without abnormal deflection.
Request of the asymmetric tooth for unidirectional drives permits improved efficiency. For the self-locking gears that are being used to avoid backdriving, the same tooth flank is used for both generating and locking modes. In cases like this asymmetric tooth profiles provide much higher transverse speak to ratio at the provided pressure angle compared to the symmetric tooth flanks. It creates it possible to lessen the helix angle and axial bearing load. For the self-locking gears that used to avoid inertial driving, several tooth flanks are used for driving and locking modes. In cases like this, asymmetric tooth account with low-pressure angle provides high performance for driving mode and the contrary high-pressure angle tooth account can be used for reliable self-locking.
Testing Self-Locking Gears
Self-locking helical equipment prototype pieces were made predicated on the developed mathematical types. The gear info are presented in the Desk 1, and the check gears are provided in Figure 5.
The schematic presentation of the test setup is proven in Figure 6. The 0.5Nm electric electric motor was used to operate a vehicle the actuator. An integrated acceleration and torque sensor was mounted on the high-velocity shaft of the gearbox and Hysteresis Brake Dynamometer (HD) was linked to the low acceleration shaft of the gearbox via coupling. The input and productivity torque and speed data had been captured in the data acquisition tool and additional analyzed in a pc applying data analysis application. The instantaneous efficiency of the actuator was calculated and plotted for an array of speed/torque combination. Common driving efficiency of the self- locking equipment obtained during tests was above 85 percent. The self-locking real estate of the helical gear occur backdriving mode was as well tested. In this test the exterior torque was put on the output gear shaft and the angular transducer showed no angular motion of insight shaft, which confirmed the self-locking condition.
Potential Applications
Initially, self-locking gears had been found in textile industry [2]. Even so, this type of gears has many potential applications in lifting mechanisms, assembly tooling, and other gear drives where in fact the backdriving or inertial traveling is not permissible. One of such program [7] of the self-locking gears for a continuously variable valve lift system was recommended for an car engine.
In this paper, a theory of work of the self-locking gears has been described. Design specifics of the self-locking gears with symmetric and asymmetric profiles are shown, and testing of the gear prototypes has proved comparatively 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 stability is very important (such as for example in automobile, aerospace, medical, robotic, agricultural etc.) the self-locking allows to accomplish required performance. Similar to the worm self-locking gears, the parallel axis self-locking gears are sensitive to operating circumstances. The locking dependability is affected by lubrication, vibration, misalignment, etc. Implementation of the gears should be done with caution and requires comprehensive testing in all possible operating conditions.