Friday, February 19, 2010

A Nifty New Invention - Reverse Osmosis Water Purification That Doesn’t Waste Water!

A reverse osmosis system that doesn't waste water?

Traditionally reverse osmosis water purification systems waste a tremendous amount of water during the purification process, typically 3 to 25 gallons of waste water for every gallon of clean water produced.

Obviously this is not very good for water conservation. But Watts has invented a way of recycling the contaminated waste water, eliminating the water normally wasted. They just pump it into the water heater.

Watts Premier "Zero Waste" ZRO-4 Reverse Osmosis System

The Watts website claims their patented ZRO-4 Reverse Osmosis System is the first ever that does not waste water. Instead of running the contaminated waste water down the drain like other RO systems, the zero waste system pumps the contaminated water into the water heater. Typically one doesn't drink hot water, and bathing washing and cleaning with it should be fine.

The instruction manual states that the ZRO-4 RO system needs to be located at least 25 feet from the water heater. I wonder why. What would happen if the RO system is closer to the water heater than 25 feet? If anyone knows why this is a requirement please let me know! What about tankless water heaters?

To me this is a brilliant idea for an invention. It's simple, inexpensive and saves a ton of water. Probably has a very solid patent that would be difficult to get around, although I haven't really studied the patents. They are easy enough to find on Google's patent search.

The level of contamination of the waste water isn't very high, and should not pose a problem unless you regularly consume hot water, something that is fairly easy to avoid.

The Watts ZRO-4 reverse osmosis system reduces Arsenic (V), Cysts, Cyrptosporidium, Giardia, Entamoeba and/or Toxoplasm, Barium, Hexavalent, Chromium, Trivalent Chromium, Copper, Lead, Fluoride, Cadmium, Radium 226/228, Selenium, TDS, and Turbidity. It also has filters since RO systems can't get every nasty out of the water.

There are some potential problems with operating the system with hot water demand systems and some hot water recirculating systems. Since the RO system connects to both the hot and cold water lines, any other equipment that also connects to both the hot and cold water lines present opportunities for problems.

Hot water circulating and hot water demand systems that pump water from the water heater to purge the cooled off hot water in the pipes, or that circulate warm water for instant hot water purposes can cause water to flow through the RO unit just as though the RO pump is running.

The flow of water though the RO system resulting from the operation of the recirc pump may increase the delivery time for hot water to reach the fixtures. With the warm water circulating systems and with the hot water demand type systems the cold water piping can end up full of contaminated waste water.

Watts also has a retrofit version of it's zero waste system which allows you to convert your existing system to a no waste system. The retro-fit system includes a solenoid valve in series with the pump used for pumping the contaminated water into the water heater.

I don’t know if a demand pump would cause water to flow through the solenoid valve backwards or not because I haven't had an opportunity to test one, but it might be a viable solution for using both the ZRO-4 and a hot water circulating or demand system...but someone needs to test it to be sure.

Overall, a great new invention at least in my opinion for what its worth.

Tuesday, February 9, 2010

Inventors Notes – Switching Electronic Air Pressure Regulation

My Asparagus harvester invention utilizes pneumatic cylinders to cut the individual spears, and the stroke length has to right on the money every time. If the pressure goes up the stroke length becomes longer, and if the pressure goes down the stroke length shortens.

Too much pressure and the piston rod will bottom out against the front cylinder head, and not enough pressure will reduce the stroke length an cause the blade to not cut all the way through the spear or even not reaching the spear at all. Allowing the piston to bottom out against the front head will eventually damage the cylinder.

The asparagus harvester has 14 air cylinders mounted on the header arranged across the asparagus bed. Each piston rod is equipped with a sharp blade with a slight bit of overlap with the blades next to it. The cylinders are angled down toward the ground and when they extend the blade severs the spear slightly below ground level requiring a stroke length of about 20 inches. Typically the extension stroke takes around 35 to 40 milliseconds.

An optical detection system locates the spears and sends a signal to open the air valve for the cylinder corresponding to the co-ordinates of the spear to be cut. The harvester is moving forward at between 20 and 30 inches per second, and so the blades must cut the spear and get back up out of the way of any spears that are not quite tall enough to harvest.

Asparagus spears emerge from the bed in a random pattern with random heights. At any moment during harvesting there may be as many as 5 or 6 cylinders operating at the same time, or none at all. You might have 10 feet with nary a spear, and 18 spears in the next 24 inches.

Because these cylinders are very fast acting they require high flow rates at a constant stable air pressure. While stroking, the cylinder will be consuming around 165 cubic feet per minute of air. Six cylinders operating at once would require a whopping 990 cubic feet per minute.

With such large swings in flow and rapidly varying air consumption the mechanical air regulator will have a significant variation in the pressure drop, which will have a detrimental affect on the stroke length of the cylinders.

We can, however, use another approach to regulating the air pressure. We can use a switching electronic air pressure regulation scheme. With this approach we replace the mechanical pressure regulator with an on or off electric air valve with a high flow rate.

We can then use an accurate analog pressure transducer to open the valve whenever the pressure drops below the set point, and shut off when the pressure is at or above the set point.

The valve has a very low pressure drop unlike the mechanical regulator. The valve can handle the flow required by multiple cylinders without the air pressure drooping that the mechanical regulators end up with.

There will be small pressure spikes or what is known in electronics as a ripple in the pressure. By properly sizing the manifold I can filter out the small pressure ripples.

For more details about electronic switching air pressure regluation for the asparagus harvester

Monday, February 8, 2010

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