Differential windlass drives: How new designs work for linear motion

Rise Robotics now sells the Rise Cylinder — an electromechanical linear actuator that (according to the company) delivers power density and reliability comparable to or exceeding those of linear actuators based on roller screws and hydraulic cylinders. Rise Robotics is currently working with select partners to bring the actuator to market through commercial production.

Shown in this video is an arrangement shown in this picture is an un-compacted version of Rise Robotics Rise Cylinder:

Windlasses: Review of the basic machine workings

Recall from basic mechanical design engineering that a windlass is an assembly to gain mechanical advantage for moving large loads. At the core of any windlass is a solid bar or cylinder (sometimes called the windlass barrel or drum) that rotates due to some input … such as manual input or that of an electric gearmotor, for example. A cord wound around the drum attaches to the load and fixpoint to allow for power transmission. Sometimes there are parallel spiral grooves on the drum to keep the flexible cord on track.

In differential (or Chinese) windlass variations, coaxial drums (with radii that are different) accommodate the flexible cord or belting that winds onto one while unwinding from the other for amplified mechanical advantage.

The linear-actuator adaptation of a differential windlass drive (sometimes called a Chinese windlass drive) is shown here. More specifically, two Chinese windlasses oppose one other to deliver push and pull motions. Rise Robotics Rise Cylinders are an engineered adaptation of this mechanical arrangement — U.S. patent 9121481B2.

Rise Cylinders are based on this differential windlass drive technology … and are driven by a brushless motor … and use steel reinforced belts for the flexible-cord element.

Rise Cylinders come in sizes that are bigger than most roller-screw linear actuators to serve large all-electric lifting and reciprocating machines. For special applications, Rise Cylinders can be customized to actuator extremely long strokes — to 60 ft. Otherwise, standard Rise Cylinders come in sizes to 650 mm in diameter; deliver thrust loads to 450 kN; and speeds to 1.0 m/sec for millions of maintenance-free actuation cycles.

Rise Robotics model RISE-CYL-095-1200-1 electric linear actuators deliver up to 9.5 kN at up to 0.8 m/sec over a service life to 1,120 km. They have a 95-mm diameter and 1.2-m maximum stroke.

Based in Somerville, Mass., Rise Robotics was founded in 2011 with the mission of developing performance exosuits. Their electromechanical linear actuator products arose from this engineering. For more information, visit www.riserobotics.com or email email@RISErobotics.com.