Why A Rotary Lock? - Failsafe Hydraulic Load Holding
When it comes to hydraulic load holding and locking, the engineering community is likely more familiar with rod locking devices, including the Bear-Loc® made by our company. Much less known is a rotary type of hydraulic lock. In this case study, we will describe a recent application and discuss various other applications.
Rotary Lock in a Flying Shear
In 1985, a rotary Bear-Loc® by York Precision Machining & Hydraulics (then known as York Industries) was sold to a customer for use in equipment called a flying shear. The purpose of the flying shear was to cut material coming off a roll. The drive train consists of an electric motor driving the flying shear through a flexible coupling. But there was a curious additional need required in this drive train.
The flying shear needs to be rotationally disconnected from its driver. This must be done quickly and accurately and then the shafts must be quickly reconnected at the correct “clocked” position of the shafts.
This machine, approximately 35 years old, was being rebuilt/reconditioned in Europe for continued use. The company using the machine approached Coupling Corporation of America (CCA), a York, PA based company, to either rebuild or supply new the complete original drive train. Fortunately, CCA had original drawings and design features of the drive train and immediately recognized the rotary Bear-Loc® and was familiar with its design and features. CCA came to York Precision knowing this was their proprietary product. They also have the knowledge and expertise to integrate with other components, in this case, the CCA Flexxor coupling.
How Does a Rotary Lock Work?
CCA President and engineer Jim H. Anderson Jr. provided this recap of the rotary The Bear-Loc® and its application:
“The Bear-Loc® provides specific features which apply perfectly for this installation. The rotary Bear-Loc® is designed to release at the instantaneous application of hydraulic pressure which allows the motor and or the shear to rotate independently from the other. This rotation is smooth, on bearings in the Bear-Loc® and without friction. When hydraulic oil pressure is released, the Bear-Loc® grabs the shaft again and torque is transmitted between the drive and the shear.
“With the hydraulic pressure still applied, if desired, the driver and driven shaft can be “timed” (put into the correct angular orientation with respect to each other) before releasing the hydraulic pressure to lock up the connection.
“The additional safety over torque feature of the Bear-Loc® is important as well. The Bear-Loc® is designed to slip at a limit torque, if for instance, the flying shear were to jam. That is, the Bear-Loc® has a designed and tested limit of torque transmission so that if torque through the drive train were to exceed the normal desired amount, the Bear-Loc® immediately slips and reduces any possible over
torque consequences to the system. This feature saves other parts of the drive train from possible damage.”
Other Rotary Lock Applications
Application possibilities are perhaps limited only by the design engineer’s imagination. Consider, for example:
- rolling applications (e.g. paper, metal, or fabric handling),
- testing (e.g. transmission testing)
- power, and
- petro-chemical applications.
There are many mechanical drive applications which for one reason or another desire a “shear pin” safety feature. Where a drive can have multiple over torque occurrences, it would be desirable to utilize a Bear-Loc® rotary lock which permits multiple events rather than needing to continually replace shear pins.
The hydraulic release and timing feature can be used in those drive train systems where, for instance, two gear type rotors need to mesh perfectly. Often these drives are designed requiring keyways to be machined on shafts after the lobed gears are rotated into position. Cutting keyways to time lobed gears is not too accurate. The Bear-Loc® can much more accurately offer this rotational “timing” feature where the two meshing gears need to be quickly and precisely “timed.”
Bear-Loc® is suited for rotary and linear applications, the latter in both tie rod and mill type constructions. It is custom designed and available as a locking actuator system, or lock-only unit, for new designs or retrofitting, whether in line or parallel. Bear-Loc® is available in a wide array of mounting options.
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Last Updated: December 10th, 2019