A new research paper has highlighted an Amazon patent showing how to transport warehouse workers inside a cage.

The patent was granted in 2016 but is making news now given the wider debate around how Amazon treats people who work in its warehouses.

Amazon says the system was never implemented and the cage was designed for worker safety.

Amazon workers paid to address the firm's social-media critics have also weighed in to defend the patent.

A patent filed in 2016 has come back to haunt Amazon just as it's under major pressure over the way it treats people who work in its warehouses.

The original patent documents depict a cage designed to carry employees around warehouses. The idea is that as warehouses become crowded with robots whizzing around carrying out tasks, it may be safer for humans to navigate these workspaces in an enclosed box.

The patent, titled "System and Method for transporting Personnel within an active Workspace," was unearthed in a recent paper by the artificial-intelligence ethics researchers Kate Crawford and Vladan Joler.

Their paper describes the design as "an extraordinary illustration of worker alienation, a stark moment in the relationship between humans and machines."

According to the patent, the contraption was designed to safely allow human workers into "protected areas."

Here's a drawing of the cage from the patent filing:

Amazon's "System and Method for Transporting Personnel within an active Workspace" design. USPTO

Though the patent isn't new, Crawford and Joler's paper caused shockwaves on social media after the drawings were highlighted by a report in The Boston Herald.

Amazon's senior vice president of operations, Dave Clark, reacted to the furor on Twitter, saying "even bad ideas get submitted for patents."

Business Insider has contacted Amazon to ask how its robot-repellent vests work.

Amazon fulfillment-center ambassadors — warehouse workers who tweet in a public-relations capacity for the company — expressed support for Amazon as well.

One ambassador wrote: "The building where I work is very safe and clean... I inquired about this cage thing and it is just one of those patents that many companies have. They may use it though.

"The way I look at it is that the cage was developed for the safety of the worker in mind. Besides this patent was from a few years ago. Many of your large companies have strange patents out there."

Another ambassador tweeted: "Amazon does not want to put its workers in cages, this patent will never be used as they found a better way to get the job done. Dave Clark himself put out a statement clearing it up!"

Big tech firms file what look like dystopian patents quite regularly. In 2017, Amazon filed a patent that would allow delivery drones to analyze customers' homes with a view to selling them more products.

And some Twitter users with no clear affiliation with the company appeared untroubled by the cage concept, saying that being inside an enclosure when working with machinery wasn't so unusual.

—Dead Vape Shop (@fatcatvapor) September 8, 2018

Amazon has come under fire recently for its working conditions, with an undercover journalist reporting that workers were peeing in bottles over fears using a restroom would waste time, though Amazon denied this.