A SMALL DIFFERENTIAL PRESSURE CHECK VALVE AND HIGGINSON TYPE PUMP
By K2MMW
Before beginning go to:
http://www.zity.biz/index.php?mx=gallery;ox=showalbum;ax=4489
Which contains instructive photographs concerning this paper. The photographs there may not be in order but are captioned to help tie this epistle together. I number these photos from right to left with the first being a picture of the completed syringe. Here I will call it Photograph 1.
The answer to reflux in any fluid system is to use a device that only allows water to flow in one direction while blocking the reverse flow. Such a device is called a check valve. It is analogous to the electrical diode that permits electric current to flow in only one way. After contemplating this problem, the author devised a low pressure check valve. These check valves are the heart of my Higginson type pump. Constructing the valves will be accomplished first. The completed unit is shown in Photograph 2 below.
Photograph 2
Completed Check Valve
Tools and Materials
The rest of this article describes how to make one for yourself from materials found in the trash barrel. Only a stick of thermal setting glue needs to be purchased.
The items required are:
1. Three, one and one half inch threaded
bottle necks cut from two plastic bottles
2. Six inches of silicon rubber tubing
3. Two threaded bottle caps from the above bottles
4. One sheet of light gauge plastic wrap
5. One thermal setting glue stick.
6. One Plastic Tee Barb ½ inch.
7. One feminine douche bulb syringe
8. Heat source such as a propane torch or alcohol lamp
9. Needle nose piers
10. Electric drill
Bottle Necks
See Photo 3
Of this short bill of materials, the most difficult to obtain are the bottle necks because they require work! They are cut with a fine toothed saw, such as a hack saw or band saw, to remove the threaded neck from the rest of the drink bottles. To do this, remove the cap from the bottle and observe that there is a small lip or flange that provides a stop for the cap. The underside of this lip is the place where you make your cut. Cut two or three of these bottle necks. Two of them will be used to make the body. The third bottle neck that you just cut is a depth gage for setting the stem so it makes proper contact with the diaphragm.
When you are finished cutting, sand the bottle neck lips be flat and square, The requirement for flatness is because this is the area where the two bottle necks will be glued together with a plastic sheet them to form the perforated diaphragm and the body of the valve. It will need to be water tight.
The Valve Body
See Photo 4
While the necks are at hand, we can put the plastic sheet between them and form the diaphragm. First lay out a sheet of plastic cut from a thin plastic bag or kitchen film etc. Next, heat the hot glue to the melting point and warm the freshly cut bottle neck lip at the same time. Apply the glue evenly to the flat surface of the bottle neck’s lip. When a thin layer of glue covers the lip, set the neck, glued surface down, onto the smoothed plastic sheet. This glues the sheet to the lower opening of the bottle neck and seals it closed. When the glue cools, trim away the access sheeting with a pair of scissors and set it aside. The second bottle neck should now have glue applied to its lip in the same manner. When the glue is on the second lip, set it on the lip of the first so that it is glued to the other side of the plastic sheet. Now the two bottle necks are glued together separated by a single plastic diaphragm that is water and air tight from both sides. After gluing the second neck to the diaphragm, let it cool.
The Diaphragm and Caps
See Photo 5 5a and 5B
The problem now is that fluid can not get through the diaphragm during forward flow. To solve the situation, a thin, red hot wire is used to melt two openings along the inside diameter of the body. These holes are approximately 90 degrees long and 90 degrees apart. This assembly now forms the body of the valve. To complete the assembly of the body, spread a band of hot glue around the outside of the joint of the two lips as seen in photographs 4 and 5. Photo 5 shows the stem in contact with the diaphragm in the left hand portion of the photo.
The Stem, Coupler and Bottle Caps
See Photographs 5, 5A, 6 and 7
Next turn your attention to the bottle caps and the thermo-plastic tubing that pierces them. Possibly the most obvious source for the two tubes is to use the barrel of a pen. Another source is a dollar store, where children's toys that are made of plastic tubes abound. (A jump rope found in such a store, supplied the author I:\with over twenty, two inch long, tube segments!) One might also try the plumbing, hardware stores or a search around one's own home for cleaning tools such as feather dusters which
occasionally have plastic tubing handles. The tube you select should also be of thermo-plastic and have an outside diameter of three eighths of an inch (10 mm). That diameter is slightly larger than the standard 5/16 inch vinyl plastic tubing that will be coupled to it.
Cutting and Modifying the Tube Segments
Cut one tube segment at approximately three inches long and the other one approximately four inches. Now, flare one end of both tube segments by warming one end of each over the slow flame of a propane torch or alcohol lamp. Insert a mandrel, I use a twist drill, the same size as the inner diameter of the tube and push the warm end lightly onto a table top and form a lip or bell shape on the end. The short tube segment is designated the coupler while the longer is the stem. These tubes may now be temporarily put aside for a few minutes while the bottle caps are modified.
Drilling the Bottle Caps
Both of the bottle caps need small holes drilled in the center of their tops. Since the tubes we will be inserting are 1/4 to 7/16 inch O.D. every attempt should be made to drill the caps to no more than three sixteenths of an inch. This is to ensure a tight fit when the connecting tubes are inserted. Start the holes by finding the center of the caps and with a small twist drill to start a pilot hole from the caps’ outside center.
See Photographs 5A and 5B
Heating the Hole
Now, the hole needs to be expanded. To expand the small hole, heat the area around the hole with a small flame. To heat the cap evenly, sight the flame through the hole from the cap’s under side. Heat approximately three seconds or
until the plastic becomes pliable. Next push a small conic shape, such as a pencil, from inside the cap and push it through while keeping the point centered to expand the hole a little more. Reheat the hole if necessary. Next center one of the plastic tubes from the inside of the cap into the warm hole and push it through. The end result should be a hole with the fillet rising on the outside of the cap and a tight fitting tube piercing the cap as in photograph 5A and 5B. Now do the same with the other cap and tube combination.
See Photographs 3 and 7
The Stem
Cementing the tubes into the bottle caps is the next and very important step. Locate the third bottle neck and screw a holed cap onto it! You are almost finished modifying the caps. The next operation is to cement the stem in place. Here again the thermo setting glue sticks seem to work best. Form a ring of glue near the unmodified end of the stem and insert it into the hole in the cap and bottle neck, depth gage combination. Here is where the contact distance between the stem and the diaphragm is set. Now, invert the assembly and push the stem down on a flat surface. The smooth end of the stem should have wiped the hot glue into place and protrude from the outside of the cap and be square with it. See Photograph 5B.
See the right hand portion of Photograph 5 and 5B
The Coupler
Turn your attention to the coupler and the procedure is nearly the same as that of forming the stem. The exception is that the flared end of the coupling tube is pulled flush with the inside of the bottle cap. The non-flared end is gets a hot glue ring and is pushed and pulled through the inside of the bottle cap. The glue is wiped to the flared end of the tube. The flare of the short coupling seats in the recess of the cap and is held in place by the glue. At this point, be sure that the tube is loosely seated in the bottom of the cap. If the coupling is pulled flush and tight with the bottle cap, the glue will be dispersed and the strength of the joint will be weakened. Be sure that the coupler portion on the outside of the cap remains perpendicular to the cap while the glue cools.
See Photograph 1
In the Higgy application, two of these valves were attached to each other by a “T” tubing connector such that the uni-directional flow was maintained. To do this, both valves must be pointed in the same direction. The base of the “T” provides an injection port for a bulb syringe forming an in line type hand pump. See Photograph 2. You will need to make two check valves like those discussed above to configure a Higginson style pump.
To use these valves to form a Higginson type pump, the assembly process is much simpler than the assembly of the valves previously discussed. The main feature of the pump is a ten ounce feminine douche syringe. To Convert the syringe for this use can be almost painful! This is because it requires the constructor to cut the tip of rubber nozzle of a newly purchased syringe. Make the cut below the exit holes in the nozzle’s end. The water supply hole in is exposed. Dispose of the end of the pipe and small holes! Insert a ½ inch tee barb’s base port into the nozzle’s channel.
In Photograph 1, you will note that a hose clamp is wrapped around the bulb where the nozzle enters the bulb. This is done to stop leakage between the nozzle and the bulb. Also, the nozzle is elastic so the clamp can not be tightened. A piece of half inch plastic tube inserted into the nozzle at the threaded end gives the clamp a hard surface to tighten against.
As before, reverse flow is prevented because both valves are closed. To start forward flow from a full reservoir or tank, simply squeeze the bulb. The outlet valve closes while the inlet valve opens to allow water to be sucked out of the tank. When constant flow from positive head pressure of the reservoir is desired at any time, simply stop pumping the bulb and both of the series valves will open.
In conclusion, I have used these valves and Higginson type pump for the for several years and found them to be durable and functional. Reverse flow and leakage can be nearly negligible but depends on the attention to detail of the construction. Since the bottle caps remain threaded and screw into the valve body a quick and easy break point for nozzle change is built in. Disassembly is quite easy and the units can be washed, sanitized and air dried for the next use.
The author invites your comments. Please address your correspondences via e-mail to: mailto:k2mmw@yahoo.com