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...offering superior strength at a reduced size and weight NASA Goddard Space Flight Center invites companies to license superior roller locking devices including a one-way bearing that incorporates Goddard's three-dimensional roller locking sprags and thrust rollers. These one-way bearings are more compact, lightweight, and significantly stronger than conventional one-way bearings. They incorporate improved lubrication paths and much lower contact stresses, creating a one-way bearing that is also more reliable and durable. The unique three-dimensional roller locking sprag provides a solution to torque-coupling locking brake and clutch applications that are too demanding for conventional sprag brake/clutches. The new sprag is lightweight and compact, while offering greater strength and durability. Its unique three-dimensional grooved surfaces lock several times more effectively than a standard two-dimensional sprag and can be used in any application where 2-D sprags are used.
NASA’s one-way bearing assembly is far superior to existing one-way bearings.
Applications for these roller locking devices include:
Traditional one-way bearings typically consist of 2-D sprags and rolling bearings, with each in separate concentric races and the bearings and sprags along a common rotating shaft. The sprags and the bearings in these devices are commonly located along the axis of the rotation of the shaft, one above the other. The rolling bearings can be spherical bearings, roller bearings, or tapered bearings, but are most often ball bearings. This new and unique one-way bearing assembly combines NASA’s 3-D roller locking sprag and thrust roller technologies to create a superior one-way bearing. The bearing assembly places 3-D sprags and thrust rollers in a common race to create a more compact and robust one-way bearing with superior locking capabilities and the ability to handle thrust loads. How it works
When the one-way bearing is in operation, the inner and outer members rotate in the preferred direction (with respect to each other). The sprag preload springs ensure that the 3-D sprags are in constant contact with the grooved races of the rotating members and produce little friction as they slide along because the spring preload is very light. These sprag preload springs are also acting as a carrier, separating the thrust rollers from the 3-D sprags. If the inner and outer rotating members attempt to rotate in the nonpreferred direction, the 3-D sprags lock instantaneously and the inner and outer members are stopped. Why it is better This one-way bearing design is stronger and more robust than existing one-way bearings, while also being more compact and lightweight. When compared with one-way bearings using pawls, it is also much quicker in reacting and minimizes backlash. Finally, because its simple design uses off-the-shelf thrust roller bearings and races, it can be produced more quickly and inexpensively.
Brakes and clutches are used in many machines with rotating parts to stop or control the degree and direction of motion of the driven parts. Brakes and clutches often are incorporated between concentric races (i.e., rotating shafts). One class of locking brake/clutch uses spherical balls or cylindrical rollers located between an inner and outer race. At least one of the races contains cam surfaces against which the balls or rollers wedge and lock to produce instantaneous torque coupling. A variation on this approach incorporates the cam shape into the roller (i.e., sprag), which rotates at a small angle to engage the sprag’s cam surfaces against the concentric cylindrical surfaces of the inner and outer races. Springs are often used to preload the sprags against the race surface so that the sprags engage and disengage instantly with no backlash. How it works
The two additional contact points increase the locking efficiency of the device, while reducing the level of sprag-to-race contact stresses. Why it is better In conventional cylindrical roller sprags, the roller contacts the races along the full length of the roller sprags. However, NASA’s 3-D roller locking sprag contacts only the diametrically opposing sides of the grooved races at the four points noted above, reducing contact stress and increasing holding power. Typical sprags also have small cam angles and, therefore, have large contact stresses in order generate sufficient holding torque. This results in devices with walls that must be thick and long and ultimately result in sprag devices (e.g., overrunning clutches) that are heavier and bulkier than necessary. Because these 3-D sprags can be produced with much shorter axial lengths, they have less mass and weight and the assemblies they are in can be small and lighter. Additionally, this 3-D roller locking sprag allows more versatility in design dependant upon the locking effectiveness needed. For example, the locking effectiveness is naturally increased over standard sprags when using the same incline and lubricants (i.e., coefficient of static friction) as usual. But, the usual margin of locking effectiveness can also be maintained while allowing, for example, the use of more slippery lubricants. Finally, the torque output can also be improved by increasing the incline angle while maintaining the usual lubricants (i.e., coefficient of static friction)—without increasing the contact stresses on the sprags.
If your company is interested in becoming a licensed supplier of one-way bearing or 3-D roller locking sprag prototypes, please contact: Innovative Partnerships Program Office
NASA Goddard Space Flight Center has patented these technologies:
(Links open new browser windows.)
This technology is part of NASA’s Innovative Partnerships Program Office, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing the One-way Bearing and/or 3-D Roller Locking Sprag (GSC-13905 and GSC-13617) technologies for commercial applications or becoming a licensed supplier of one-way bearing or 3-D roller locking sprag prototypes. For information and forms related to the technology licensing and partnering process, please visit the Licensing and Partnering page. (Link opens new browser window)
If you are interested in more information or want to pursue transfer or prototyping of this technology, please contact: Innovative Partnerships Program Office
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The simple design of NASA’s one-way bearing incorporates an inner and an outer rotating member coupled by a set of thrust rollers and a set of sprags. It also incorporates sprag preload springs that provide independent spring preloading to each of the 3-D sprags. These springs act as a low friction carrier as well as ensure that each sprag locks into position immediately if the one-way bearing attempts to move in the nonpreferred direction. Two sets of thrust lips are attached to the inner and outer members to enable the thrust rollers to handle thrust (axial) loads.
NASA’s innovative 3-D roller locking sprag has a tapered periphery and replaces the concentric, cylindrical surfaces of the inner and outer races of the brake/clutch with grooves, in which the 3-D sprag fits. This geometry creates four points of locking contact—two between the outer taper of the 3-D sprag and the outer grooved race, and two between the inner taper of the 3-D sprag and the inner grooved race—twice as many as with conventional, simple ball-based locking brakes/clutches.
