After many years of searching for the perfect telescoping linear actuator, I would like to share my discovery of the I-Lock Spiralift 75 (ILS75) prototype by Paco Spiralift. The ILS75 has a compact form factor (10x15x15 cm) that can telescope out to 1.6 meters while lifting a 175kg load (350+ lbs). It relies on a system of interlocking horizontal and vertical metal bands that "unroll" to lift a load, a process best illustrated in the videos embedded below. The ILS75 is just one Spiralift offering; others range all the way up to a goliath version (Spiralift ND18) that can lift an 11,000 kg load 12 meters (25,000 lbs to 40 ft). To date, Spiralift mechanisms have been applied to theater stage-lift systems and automotive lifts. At Hizook, we believe robotics is a compelling application, especially as a robot's vertical spine (eg. on EL-E, Cody, and PR2) -- increasing the robot's effective workspace to include floor and tables, and also for compact and easy transportation. As such, we're working with Paco Spiralift to gauge roboticsts' interest and vet the technical specs of the ILS75 -- tell us what you think in the comments.
Before we look at the ILS75 in particular, let's look at how the Spiralift mechanism actually works. It is (apparently) referred to as a helical band actuator, and was awarded a US patent (4875660) in 1989. Here is how it works:
The new Spiralift prototype (ILS75) is what caught my interest. From Paco Spiralift's ILS75 webpage:
The I-Lock 75 principle of operation is quite simple: two stainless steel bands engage as they rotate to form a remarkably strong lift column resulting in a rigid structure. Its self contained electric motor provides pushing or pulling action with infinite adjustability. The new 100x150x150 mm model, shown here, has travel of 1600 mm and a load capacity of 175 kg. (see product specifications sheet of I-Lock 75) Since higher travel and higher capacity are possible, it is perfectly adapted to a whole new range of applications.
More details are available in the datasheet. We have also been informed of one important caveat: these units are limited to around 25,000 cycles (presumably due to metal fatigue?). Obviously, by now you're now wondering about price. Initial inquiries suggest a MSRP of $1,000 per unit in small volumes, and potentially as low as $400 in volume -- though these are subject to change as development continues, and it wouldn't surprise me if the prices end up higher due to obvious value propositions. For example, these prices are in-line with traditional linear actuators (eg. Festo) and are an order of magnitude lower than competing telescoping linear actuators (eg. Zippermast).
Does this type of actuator interest you? Let us know your thoughts in the comments or via contact page so that we can communicate them to Paco Spiralift. I'll go ahead and kick off the conversation:
A number of prominent mobile manipulating robots (eg. EL-E, Cody, and PR2) incorporate a vertical linear actuator (a "spine"), increasing their effective workspace to encompass floors, tables, and shelves. Unfortunately, lead- and ball-screw mechanisms are usually employed, and they have a fixed height. This dictates a "tall" robot that causes major relocation headaches -- you either ship the robot in a moving truck or stuff a 6-foot-tall robot into the back of a car. [In this regard, I speak from experience: it's a pain! I have transported EL-E to and from my home in the backseat of my Honda Civic!] If the robot could shrink for easy transportation, moving research out of the lab and into homes becomes a less ungainly proposition.
I'm sure there are probably numerous applications for a low-cost plastic Spiralift too. I'm curious to learn about the feasibility of such a device (fatigue problems?), but I'll leave that discussion for another day...