The military is keen on supporting the research and development necessary to produce any security equipment that will protect soldiers and civilians working in stressful places under stressful conditions. For example, when hiring local men and women for work details of any kind in militarized zones such as Afghanistan and Iraq, there is always the danger that the person hired may be carrying a gun or bomb on them while entering the work area. Knowing that these hires are safe to work next to is imperative to the safety of U.S. soldiers.

The development of backscatter-based body scanning was in 1992, and the technology has been improving ever since. As with all new equipment, the evolution in usability typically means that it must get smaller, lighter, and easier to transport and set up quickly. In the case of military use, deployment from the back of a Humvee or dangled from a helicopter and surviving is an added bonus.

Backscatter imaging systems are very similar to the laser scanners at supermarket checkout stations. A thin beam of X-ray light sweeps across the object being scanned and sensitive detectors measure the instantaneous reflected light (backscatter). Computers piece together a mosaic of this reflected energy to form the image. By using X-rays instead of lasers, backscatter body scanners can see through clothing, which does not reflect much X-rays, and forms an image of the much denser and more reflective body beneath. Fortunately, there is very little radiation emitted during a scan because the X-ray beam is very small and sweeps across the subject’s body so briefly. This also means that the acquisition of images is very quick; taking only a second or two to scan a person.

Design of full body scanners are to see through clothes and are notorious for their ability to expose some embarrassing facts. They are also the most advanced and reliable technology for finding hidden weapons and contraband.

Simulation of a soldier standing in front of a backscatter-based body scanner

Mechanical Motion
One of the more interesting aspects of the latest backscatter-based scanners is the mechanical motion system. After all, the mechanical portion can make or break the ruggedness of the design as well as the matching need for being lightweight and portable. Add to this concern the requirement that a single, minimally-trained soldier can assemble, quickly, a scanner for operation, and you have an interesting design challenge.

The staff at Jamco Engineering, located in Cottage Grove, OR, have been providing innovative solutions for radiographic equipment design for more than 20 years. They have developed everything from sophisticated medical, scientific, and industrial scanner systems to component-level designs, having earned a solid reputation in that industry. The company uses the latest CAD and CAE design tools, offer versatile in-house prototype and manufacturing capabilities, and can therefore produce a cost-effective end product for their customers much more quickly than other sources.

Therefore, when they saw the challenge of designing a mechanical motion system to meet the needs of military use, they set to solving the problem with their usual ingenuity and passion for the work.

First, they needed a mechanism that would vertically translate the X-ray source, with its high-speed rotating collimator, along the entire length of the person’s body. “The X-rays need to sweep the subject at speeds of more than 40ips, and at a very high duty cycle,” says James Carver, president, Jamco. “It also has to tilt about ±45º as it moves.”

To manage that motion, the company developed a linear drive with an ‘S’ shaped cam to control the tilt.

“The tilt angle,” according to Carver, “has to stay proportional to the vertical motion or the image will be distorted like in a carnival fun-house mirror.”

Top: The elevator mechanism for the full body scanner has to operate smoothly as well as maintain the perfect angle in reference to the person scanned. Middle: iCamFollower mounted on the backside of this mount, are running on lightweight aluminum rails. Bottom: Intech’s iCamFollowers and rollers provide long operating life and smooth, quiet operation with no lubrication, which was ideal for backscatter-based scanning devices.

The second challenge for the company was to find suitable cam followers (rollers) for use on a lightweight aluminum guide rail. “These rollers had to operate quietly, in extreme environmental conditions, including high humidity or sub-zero temperatures, at high speed, be maintenance free, and have a long life,” Carver explains. “All of the rollers we looked at were inadequate in many ways until we found Intech iCamFollowers and chose them for our design.” Metal cam followers were not an option because they are noisy, require periodic lubrication, produce vibrations that can distort the image and wear out the Aluminum rail. Other plastic cam followers do not have the load capacity and easily develop flats, rendering them unusable.

Intech iCamFollowers are precision machined from the company’s Power-Core material and are fitted with precision ball bearings. They do not require lubrication, run quietly, resist chemicals, and retain precise dimensions in varying environments.

Using proprietary engineering calculations for the scanner application, Intech engineers designed the cam followers to last more than 100 million rolling cycles, eliminate lubrication and unnecessary noise, and resist chemical or environmental damage.

Also important for the backscatter-based body scanner is that the rollers do not develop flats under pressure or during transport. The rollers also absorb shock and vibration, maintaining precision for smooth movement required to produce a clean image. Bonus specifications gained from the use of the Intech components was the elimination of the Aluminum rail wear during heavy-duty cycle operations such as those needed for the body scanning system.

Although cost was not necessarily an issue when considering which components were right for the system, Jamco found that the Intech parts were 20% less expensive than other, inferior rollers they had found.

“Furthermore,” Carver states, “the rollers we bought from Intech use higher-grade and longer lasting bearings than found in most off-the-shelf metal components.”

In conclusion, when designing critical security systems, the right component choices are as important as a great mechanical design.

Intech Corp.
intechpower.com
 

JAMCO Engineering
jamcoengineering.com