Mechanical torque limiters have been employed for many years as a simple and reliable means of torque overload protection in case of machine jams and crashes. They provide sound insurance against costly machine down time resulting from broken tooling, components, etc; and not to mention replacement of expensive, long lead time components. For this purpose, ball-detent style torque limiters have proven to be a compact and very dependable form of overload protection, reacting quickly (<3msecs) and accurately (+/- 5% of preset torque value). Most designs also offer zero-backlash and a high repeatability in terms of rotational position accuracy after re-engagement.Ball-detent torque limiters normally incorporate a series of ball bearings, driven by a retaining ring machined around the base of the unit, and spring loaded into conical detents on a hardened steel output plate. At torque overload, the balls overcome the spring load, and roll out of their detents, allowing the output plate to spin freely over an integral bearing. The output plate is normally either a piloted flange or a flexible coupling for connecting to (and disconnecting from) another shaft.
While ideally suited to applications where release of the torque limiter takes place in emergency cases, occurring occasionally, they can not be disengaged repeatedly as a part of a process, due to wear of the detent plate which takes place after roughly 1,000 revolutions in its overloaded condition. Utilizing the same principle which has been used in air ratchets in the automotive and other industries for decades, the ESL nests the ball bearings between an additional set of ball bearings, rather than into detents in a hardened steel plate. The ball bearings in the ESL roll over each other, reducing impact, and evenly distributing remaining stress around the surfaces while they spin. This significantly increases the number of overload releases the torque limiter can withstand, making it unique in the industry.
Currently the ESL is available in the form of an elastomer insert coupling, which is a low cost but robust and backlash free form of flexible coupling. They are however designed for specific OEM applications and there is a certain degree of flexibility in design when manufactured in volume. Currently torque overload values from 0.1 – 1,100 Nm (0.885 - 9735 in lbs) and shaft bore diameters of 3 – 70 mm (1/8 to 2.75 in) are available.
Next Pump Bearing Accommodates Higher Thrust Loads
BRIEF INTRODUCTION
Cnbearing is the No.1 bearing inquiry system and information service in China, dedicated to helping all bearing users and sellers throughout the world.
Cnbearing is supported by China National Bearing Industry Association, whose operation online is charged by China Bearing Unisun Tech. Co., Ltd.
China Bearing Unisun Tech. Co., Ltd owns all the rights. Since 2000, over 3,000 companies have been registered and enjoyed the company' s complete skillful service, which ranking many aspects in bearing industry at home and abroad with the most authority practical devices in China.
