Guest Column: What's A Curb Box Charger?
I have been surveying for almost 20 years now, and it is rare that some new technology comes about that I have not heard of.
Sometimes, that new technology is only new to me. I had one of those moments when I first started surveying and we were searching for a corner. The older guy on the crew with me kept asking me if I got a dip, and I was so confused. He didn’t dip, and I was starting to think he was off his rocker. Finally, I asked what he was talking about, and we laughed as he reminded me of my age and then explained what a dip needle was. To this day, I love telling that story.
Well, the same thing happened the other night at a remonumentation peer group meeting. One of the local surveyors was presenting a corner for review, and during his presentation mentioned that he couldn’t find the corner he was looking for, so he “charged the intersection.” I sat back confused, but bit my lip until he was done presenting. Then, luckily, another local surveyor looked at him and asked what he was talking about. As with “the dip needle debacle,” this led to laughter and how young I was and how exactly you “charge an intersection.”
One of the surveyors actually left the meeting, went to his truck and brought in the “charger.” I expected to see something from the 21st century, something that sits alongside the ground penetrating radar (GPR) unit, or next to the drone or the robot. It was none of the before-mentioned items. Actually, it was an odd-looking heavy piece of metal with a wooden handle sticking out of the side. For a long while, the meeting came to rest as we examined this contraption and an explanation was given by the surveyors who knew what it was and how it worked.
The heavy metal contraption had a small tag on the top that labeled it as a Miller Curb Box Charger with U.S. Patent Number 2,817,795. The surveyors gathered said how rare these were and that they have looked for them on the Internet but the search was futile. At this point, I was on a mission to find a curb box charger, and to find out how it worked and who invented the thing and why. The meeting ended a few hours later and, immediately upon getting home, I was scanning the Internet for the patent paperwork and for a charger itself.
The curb box charger was invented by Basil Miller, of Elkhorn, Wis. The original paperwork was filed on April 4, 1952, but the patent didn’t get recorded until Dec. 24, 1957. Born in Newton, Iowa, Miller was an avid inventor and businessman, but also the Superintendent of City Utilities in Elkhorn. One of his many inventions was the wind power generator. With this invention, he founded the Miller Motor Company, which was later renamed the Wind Power Light Company.
According to the patent, “This invention relates to a curb box charger and particularly to a marking device to apply a magnetic charge to hidden metal objects so they may be readily discovered by means of a magnetic needle.” Miller continues, “It frequently happens that these boxes or outlets become covered with dirt or paving material, or in the winter time with snow and ice so that it is impossible to find the devices without an excessive amount of experimental digging. It is known that elongated metallic objects such as pipes or curb boxes have a tendency to be magnetized by the earth’s magnetism. However, it is also known that the reluctance of the material of which these boxes are composed substantially defeats any magnetization thereof by means of the earth currents. However, when the earth currents are aided by means of a magnetizing device, such devices are easily magnetized, and because of that, the said reluctance retains the magnetism over a considerable length of time — even over a period of years.”
We have all searched for that PK nail, knowing it was there, but could not get a good tone on it. I personally have also had #5 rebar, 36 inches long, with absolutely no magnetic field at all. A few months ago, we actually nicknamed a troublesome harrow tooth with no tone the “Toneless Tooth.”
The patent continues, “The present invention provides a charger adapted to assist in producing magnetization of buried metal objects, particularly elongated metal objects, so that they may have a material magnetic influence and may be readily determined by means of a magnetic dip needle.” At least now I know what a dip needle is … or else the confusion would have continued.
How It Works
The actual charger works by having a super strong magnet inside a magnetized tube with a brass, non-metallic end. The super strong magnet on the inside is on a moveable plunger and can be “activated” by moving the plunger up or down. When the plunger is down, it magnetizes a limited area underneath the charger. If you do this enough times around an intersection, you have successfully “charged the intersection.”
The more technical terms straight from the patent document are as follows: “The structure, according to the present invention, provides a magnet of high permeability such as the magnets made of Alnico or other high permeability alloys. To allow proper utilization of such a magnetic device, a shield in the form of a tubular guide of magnetic material is provided and means is provided for locating the magnet within the shield when it is not in use. In order to use the device for increasing the magnetization of a buried metal object, a non-metallic end, such as a brass tube, is applied to the shield and means are provided, such as a handle, for projecting the magnet into the tube. If desired, a magnetic piece may be applied at the end of the tube to serve the double purpose of a magnetic tip and an anchoring means for retaining the magnet in the non-magnetizable guide.” Alnico magnets are made to be permanent magnets made of aluminum, nickel and cobalt, thus forming “al-nico.” The only stronger magnet is one comprised of rare earth elements, and that didn’t come about until the 1970s. Therefore, the Alnico magnet was the strongest magnet around at the time of the Miller Curb Box Charger.
The only downfall of “charging the intersection” is that any ferrous object (i.e., bottle caps, slag, etc.) will be magnetically charged and may give a false tone to the user. The clear advantage is you may also find that “lost” section corner you have been searching for or that troublesome “Toneless Tooth.”
So, the next time you go to call out the GPR guy or the backhoe guy, maybe just thank ol’ Basil Miller and use a curb box charger — if, that is, you can get your hands on one.