The new PF (PowerFlex) Series of couplings is Helical’s latest and best offering yet to the world of power transmission products. By incorporating features that make practical sense into this versatile, maintenance free coupling, Helical Products Company is now able to compete head-on in a highly competitive marketplace with a product that will perform superbly in customer applications.
The PowerFlex is essentially a very cost effective coupling/coupler, the benefits of which include no lubrication, no maintenance, no keyway requirements and zero backlash. Plus, the product provides more torque for less money than past Helical power transmission coupling offerings of the same size range.
Four key elements have been incorporated to create the PowerFlex: the HELI-CAL® Flexure, the convenience of removable tapered bushings, high torque capacity (up to 1800 lbin), and substantial misalignment capability.
Early on in the PowerFlex design process, it was recognized that the time tested and proven HELI-CAL Flexure should be utilized as the key coupling component. The HELI-CAL Flexure is a flexible helix (curved) beam machined from one piece of material into a specific configuration that incorporates special design requirements, performance features and characteristics. Use of the "Flexure" simplifies the manufacturing process, lowers production costs and reduces lead times, which means faster delivery and lower prices.
After reviewing various combinations of coil thickness, number of coils, number of "starts" and flexure ID’s, we arrived at a double start HELI-CAL Flexure configuration that accommodates sizable misalignments, and provides substantial torque capability, high torsional stiffness, and reasonable pricing. This represents value for the customer, which is always a key goal when we develop a new series of couplings.
This innovative design provides a flexible shaft coupling that can compensate for many operational variables, such as parallel offset and angular misalignment present anytime two shafts are being attached. The PowerFlex’s unique flexing element also accommodates axial motion between two shafts.
The PowerFlex is available in anodized aluminum and stainless steel. Shaft sizes range from .50 to 1.75 inch diameter. Maximum torque ratings go from 250 lbin for the 2.0 inch OD aluminum to 1800 lbin for the 3.0 inch OD stainless steel coupling. Maximum torque values are divided by a service factor to determine the proper coupling for a given application.
The new couplings are configured with two flexing elements, each consisting of two curved beams spaced 180 degrees apart. Each curved beam is a spiral configuration that provides a beam long enough for good flexibility, but short enough to be torsionally stiff. This high torsional stiffness is exceedingly important in motion control systems where position accuracy is critical. Each double beam element can bend 2 degrees for a total of 4 degrees angular misalignment. The flexing elements are used in pairs to allow for parallel offset between two shafts.
The double beam configuration of the PowerFlex provides a stability that makes it well suited for high rotational speed applications up to 6,000 RPM. Since all the flexing for misalignment is taken up by the beams, (made from a single piece of material), the PowerFlex is perfect for those troublesome power transmission applications. The single piece flexing element makes this coupling essentially maintenance free. Besides featuring high torsional stiffness, the PowerFlex is also backlash free, making it particularly well suited to high torque motion control applications. The PowerFlex offers considerable savings in maintenance costs (there are none) in applications where lubrication access is restricted or near impossible.
A tapered bushing attachment provides a positive method to hold the coupling to the shaft. The bushing’s taper angle is low enough to give good concentricity and torque transmission capacity yet high enough to release the bushings from the coupling easily. Installation is achieved by sliding the bushing up the shaft, and placing the coupling into position. The bushing is tightened by progressively torquing the hex head screws to the specified torque in a star pattern. This star pattern tightening sequence is then repeated on the other end to complete the installation. Since the holding capacity of the tapered bushing is more than the maximum torque capacity of the coupling, keyways are not necessary.
Removal of the PowerFlex is accomplished by removing the hex head screws from both ends. The tapered bushings are released from the coupling by threading two of the hex head screws into the threaded holes of the tapered bushing flange. By tightening the hex head screws the tapered bushing is pulled from the coupling and the friction taper attachment is released.
Because we machine precision bore sizes into the tapered bushings, PowerFlex couplings can be assembled quickly to suit customer needs and delivered fast. Customers also may make coupling bore size changes themselves.
The PowerFlex PF series is available in both inch and millimeter bore sizes in aluminum or stainless steel. Many sizes are available for immediate delivery.
The new PowerFlex power transmission flexible beam coupling from Helical may well be the answer for a wide range of motion control applications, particularly where designers want a coupling that is easy to use, is maintenance free, and has a very long life. | 
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