Inventing a Selective Asparagus Harvester

For the last week or so I have been trying to do some life cycle testing on the pneumatic cylinders that we are going to use for the next asparagus harvesting machine we build. The cylinders should be able to do about a million strokes before the need to be replaced.

The machine has a row of pneumatic cylinders, or often referred to as air cylinders, arrayed across the asparagus bed. As the machine moves forward a sensing system locates the spears and tells the air cylinder lined up with the spear when to cut.

The cut signal causes the piston rod to extend from the cylinder at high speed with about 18 inches of stroke. It takes less than a tenth of a second for the cylinder to extend to full stroke. On the end of the piston rod is mounted a blade that cuts the spear.

I set up a fixture out in my garage for testing the cylinder. I’ve got it mounted to a frame similar to how it will be mounted on the asparagus harvester, pointed down at the ground at around 45 degrees.

I filled an asparagus crate or lug box, lined with plastic, full of dirt from the back yard. I placed the crate of dirt so that when the cylinder is extended the blade goes about two inches deep into the soil.

I actually went to the grocery store and bought a bunch of asparagus to test the cutting ability of my blades. I wanted to see if I could detect a difference between a blade with a V notch in it, a slanted edge like a guillotine, and an arrowhead type blade.

I tamped the soil down till it was nice and firm, and then used a dowel to make a hole just big enough to get an asparagus spear into. Then I pushed a spear into the hole and tamped the dirt down around it. I lined up three spears so the blade would contact the first spear while in mid-air, the second spear right at ground level, and the third spear would have the cut line about an inch below ground.

I tried this with all three blade types, and I could find no difference at all in the cutting ability or anything else. The blades sliced through all three spears like they were made of butter. There was no deflection or twisting of the blade, so my new secret method of preventing blade rotation seems to work well.

Since revealing details about an invention online would compromise my patent rights I can’t go into details about the new method I am using to prevent the blades from rotating out of position.

I would like to do the life testing at 150 psi, but my compressor only goes between 120 psi and 135psi as it cycles. So I set the air pressure for the testing at 120 psi.

I’m interested in the life of the seals, and whether the piston rod ends up breaking due to metal fatigue. The load placed on the end of the piston rod by the blade and guiding assembly is offset from the center of the piston rod.

On the down stroke the pneumatic valve reverses the direction of the air to the cylinder before the cylinder reaches the physical end of its stroke to prevent damaging the cylinder. On the return stroke the piston hits the rod end of a smaller cylinder screwed into the rear head of the cutting cylinder to act as a spring and absorb the shock loads.

My compressor can just barely keep up with the cylinder if I fire the cylinder every 20 seconds. It’s going to take a long time to get anywhere near a million strokes. I need a much bigger compressor.

To cycle the cylinder I used a 12f675 micro controller chip, an 8 pin chip with a microprocessor, memory, and various interface modules like analog to digital converters, comparators, and counters all included. Even an accurate clock is built in. Learning to program and use these microcontroller chips should be in every inventor’s toolbox.

I programmed the chip using a basic language. I used a breadboard, a couple of pots and a voltage regulator etc along with the chip to create an automatic cycling controller. It has two pots. One pot controls the time between firings and the other determines the length of the pulse sent to the air valve. The longer the pulse the longer the stroke produced by the air cylinder.

I’ve tested a whole lot of air cylinders with this method and I’ve yet to find one that would even go 10,000 cycles without developing a problem. I think this time I’ve got an air cylinder that will hold up for that million strokes I need.

These new cylinders I’m using have a 1” diameter bore. The cylinders I’ve used previous had a 1-1/2 inch bore. There is a big difference. The smaller surface area of the piston means the force is much smaller. The acceleration is determined by the force, and the new cylinder is much more sensitive to variations in pressure. That is something that the asparagus harvester invention will have to address.

In a future article I will describe in some detail the pressure problems and the special electronic air pressure regulation system I intend to use for the machine.

To learn more about my selective asparagus harvester invention visit: Selective Asparagus Harvester

Future Million Dollar Inventions and Ideas

Want to invent that million dollar invention or idea and be set for life? It’s not terribly likely that you can do such a thing, but it’s not out of the question either.

History is full of individuals who achieved great wealth with a new invention or a new idea. Ray Crock who franchised Mc Donald’s, Steve Jobs and Apple computer, Bill Gates and his operating system, snugglies, spanks, and someone is even making a fortune because he came up with the idea of slip on cardboard coffee cup holders so you don’t burn your fingers while holding that paper cup latte.

Here are the areas where I think the small individual inventor or innovator has the best chance of coming up with that revolutionary device or idea that will make him or her independently wealthy.

Harvesting Machines for Fruits and Vegetables

Very few fruits and vegetables are harvested by machine. There are tomato harvesters and potato harvesters but not much else for fruits and vegetables. If someone can com up with a harvester for apples or oranges or similar fruit the will make a huge killing. It will truly be a million dollar invention.

Other crops that are exclusively hand harvested are asparagus, all kinds of citrus, squash, brussel sprouts, cauliflower, and man others. I’ve almost got an asparagus harvester working, you can see my latest version at my asparagus harvester website.

Energy Production

Obviously energy is always going to be needed and with oil eventually running out there are many new competing technologies for generating electricity. Opportunities abound with areas such as wind power, ocean wave power, solar cells, biofuels, and more. Figure out a way to generate electricity that costs less than generating electricity with oil or gas and you have a winner.

A Better Razor

Just image how much money you can make selling razors. Nearly every man and woman in the US and many other parts of the world shaves. How about a new kind of razor that you could use to get a comfortable and close shave with just plain water? Even better would be a razor like the above that needs a new blade every week. You could have millions and millions of customers purchasing replacement blades weekly or monthly.

The Internet

First there was America Online, soon there was ebay, craigs list, facebook, twitter, and god knows how many other social networking and other online methods of making money. All of the previous mentioned items started out as an idea. You can have ideas too. Come up with a great online game that everyone wants to play. My wife is currently addicted to a farming game on facebook I think. Find some new way of helping the masses communicate with each other is another idea, and one will probably emerge this year in my opinion. Flex your creativity and come up with the next big thing on the internet.

Geriatric Products

Anything that helps older people get along as they grow old should be big. Soon the baby boomers will all be old, so find a way to make life easier for them. This could involve the internet and some sort of social media thing too. Interesting areas for new devices include things that make bathing easier, taking medications and keeping track of medications, exercise equipment, sleeping aids, and all sorts of other convenience items.

Cooking and Food Preparation

Everybody eats and they eat every day. Come up with some food preparation or cooking device that makes preparing or cooking food easier and then sell it on those infomercials. There is a lot of money in it, just come up with something simple and clever that makes a kitchen chore easier or quicker.

Water and Energy Conservation

As previously mentioned, energy is big. Find a good inexpensive method of saving energy. Saving water is just as important and will only get more important. Find a new way to desalinate water, or purify water, or a way to save large amounts of water.

These are just a few suggestions, there are countless others awaiting your discovery. Go forth and Invent and Innovate! Be the next one to come up with that million dollar invention or idea!

Outsourcing To China – Problems Crop Up Continued…

We outsourced our pump manufacturing to China, due to our inability to find a manufacture in the US that could provide us the pumps at a price we could make a profit with. It’s not such an easy process. Good communications are critical, and so if you have to deal with a very small Chinese manufacturer you need a good go-between person who is fluent in both English and Chinese.

We were having a problem with a seal, well not us, the Chinese manufacturer. We were life testing the seals for the pump, as was the manufacturer. His seals consistently failed after a short time. Using the same parts and test procedures, (we thought), our tests were working out just fine.

I finally after weeks of going back and forth trying to find out the details I asked him to send me one of the “failed” seals.

It turns out that the manufacturer meant “leaked” when he said the seal “failed”. We wasted over a month trying to figure out what was making the seal fail before we found out it wasn’t a seal failure after all. It was another part that was failing and causing the leak, not the seal. It turned out they were testing with a slightly higher pressure than we were, which caused a plastic part to fail.

Good translation is obviously important when you are dealing with a manufacturer on the other side of the globe.

Injection Mold Tooling Problems

We have found the tooling for our plastic injection molded parts are somewhat sloppy. The parting lines are all obvious and slightly out of place, the ejector pins don’t all land on the surface they are intended to, everything is done kind of half-assed if you ask me.

Keep in mind, this was a very low budget, and with our limited funds we didn’t really have a lot of choices. The tooling works and produces parts that work, but they aren’t very pretty.

Getting code approvals in China

Working with ETL testing labs in China was just as difficult. I had to argue constantly with the Chinese engineers who worked at the ETL facility in China. Thank god for the Internet! I always won the arguments, but it took a lot of work researching and supplying documentation to the Chinese engineers.

I remember one disturbing argument; the Chinese engineer was telling me the fuse I was using for the motor was too small and needed to be bigger.

What? Bigger? How is a bigger fuse safer? It was a very surreal experience. Fuses take time to burn out. If a fuse is rated for 2.5 amps, and you run 2.6 amps through it, it may take several hours to blow. If you run 3 amps through it, it may take 30 minutes to blow. If you run 10 amps through it, it will blow in a second or two etc.

Our fuse was to protect against “locked rotor” conditions in the motor. Locked rotor is where the motor shaft is held and not allowed to rotate. Our locked rotor current would blow the fuse we were using in about 2 seconds, well before anything got hot enough to cause a fire. The fuse they were specifying would have taken several minutes to blow and danger of fire would be very real.

They finally relented and allowed us to use a fuse smaller than what they wanted but still larger than we would have liked. The one we use blows in less than 10 seconds at locked rotor conditions, but I would rather it blow in less than a second.

I’ll have more Chinese outsourcing stories in the future… some good, some bad, and some just plain funny.

More about our outsourcing experience

Inventing an Asparagus Harvester – 30 Years of Prototypes

I first decided to invent a selective asparagus harvester in about 1972. I asked my dad one day if he knew of something that needed inventing… I was bored. He was a farmer and an asparagus grower. He told me they needed a mechanical asparagus harvester that would just harvest the ripe spears; a selective asparagus harvester.

Not knowing any better I decided I would build one. At the time I was about 21 years old, fresh out of the army, and pretty good with electronics. I had a ham radio license when I was about 13 years old, built my own transmitters and receivers, and could fix anything from a car radio to a color TV.

I had read about a new kind of imaging device, I think it was one of the first CCD chips. I don’t remember all of the details, but the camera had basically 16 rows and 16 columns of light sensitive elements, and I decided to use that to detect the height and location of the spears on the bed, and I would use blades attached to air cylinders aimed toward the ground at about a 45 degree angle. I used eight cylinders arranged in a row across the bed, and when the camera spotted a spear tall enough to cut, it would activate the valve and fire the air cylinder that was lined up with the same column as the spear.

A friend of mine and I built a little demonstration prototype that had a little gas powered air compressor built out of channel and angle iron and 4 motorcycle tires that we pushed by hand. It had the camera, air compressor, 4 cutting cylinders and a crude pickup device that would grip the spears as they were cut.

That first prototype was enough to interest a local machine shop that decided to take risk of developing a selective asparagus harvester. They hired me for $2000 a month to oversee the development and took a 50 percent share of the rights to the machine. We spent the next ten years working on it, coming up with a new prototype each year.

The camera turned out to be unsuitable for the task, and during those years I tried just about everything you could think of to detect those stubborn spears of asparagus. I tried little wire bales that hung down from above, beam-breaking photo electric sensors, retro-reflective optical sensors, magnetic switches with plastic paddles, and even a Reticon line scan CCD camera, but all had serious drawbacks.

I really wanted to try a laser for illuminating the spears due to the precise position information I could get by using a laser shooting across the bed. It would be able to give me much more accurate information about where the spear was located on the bed and it’s height. But at the time lasers were several thousand dollars, and not nearly rugged enough to mount on an asparagus harvester.

Asparagus spears can be very delicate, and on cold mornings it is very easy to break a spear by just nudging it a bit. So you really don’t want to use something that has to contact the spear to detect it. Using through-beam sensors required mounting the emitter and receiver at the height of the spear you wanted to harvest. If you wanted to cut nine inch spears you mounted the beams nine inches above the bed. Harvestable spears would range from nine inches to about 16 inches on hot days. The longer spears fortunately are harder to break.

We used extremely thin sensors to avoid touching the spears, but you could still see the occasional spear break as it made contact with the sensor itself.
Another problem with sensing the spears was the fact that asparagus spears can lean in any direction, and significantly throw off the targeting of the spear. At the point where the spear reaches the nine inches off of the bed, it can be several inches to one side or to the front or back of where the spear actually emerges from the ground. That makes it a whole lot harder to cut the spear. Especially if the blades are narrow.

In 1984 we gave up the project due to lack of interest on the part of the asparagus growers. The machine was a self-propelled 3 row selective asparagus harvester. It wasn’t perfect yet but it did harvest asparagus.

At that time we used beam-breaking for sensing the spears; I think they were 4-1/2 inch wide channels the spears had to pass through.

The sensing of the spears and locating them were not the only problems we had in developing a selective asparagus harvester.

My next blog entry will discuss the difficulties we had with the air cylinders. And some of the inventive ways we found to address the problems… and why most of them did not work.

The Old Inventor Guy