Switch Activated Balloon Inflater


Requested Project

We would like a device that will use switch acess to blow up small ballons.  The device needs to be able to be run by a switch and blow air into a balloon.  Hopefully this device would not be very big.  We would like as soon as you can do it.  

Design Notes

A switch operated device to inflate balloons has been completed and will be delivered to the client around the end of October, 2006.

The balloon inflation assembly is composed of a small electrically powered bellows pump which is driven from 4 D-size flashlight batteries.  The output of the pump is coupled with automotive vacuum hose to a tapered nozzle which engages the neck of the balloon.  Serrations are provided along the taper of the nozzle to capture the O-ring like tip of the balloon neck to prevent it from sliding off during inflation.  The taper of the nozzle will accommodate neck inside diameters from about 3/8 to 3/4 in.

Balloon inflation is controlled by a timed switch or a push-on, push-off switch that is plugged into a jack provided on the side of the package.

Parts used to construct the unit are as follows:

Assembly package ? Radio Shack #270-1806  4?x 6? x 2? project enclosure made of ABS plastic. Cost: $4.99

Nozzle:  Machined from 3/4 ? brass rod, tapers from 3/8? to 3/4? over about 1 3/4 inches of length, serrations about 0.05? deep are provided at 1/4? intervals along the taper to capture the balloon neck.  The nozzle assembly is cut from the bar at 2 5/8? overall length and center drilled from both ends.  The nozzle end is drilled to a depth of 2? with a 3/16? bit.  The mounting end is drilled to a depth of 1/2? with a #21 drill and tapped with a 10-32 bottoming tap to accept the mounting machine screw.  The nozzle assembly is cross-drilled to the center of the rod at 2? from the nozzle tip using a 1/8? bit.  This hole communicates with the hole running the length of the nozzle to bring air into the nozzle.  A short piece of brass tube with 1/8? OD is soldered into this hole to provide a nipple to engage the vacuum tube that brings air from the pump to the nozzle.

Batteries:  4 D-size alkaline flashlight batteries connected in series to provide 6 volts for the pump.  These batteries have a rating of about 14 Ah and should supply the 100 ma requirement of the pump for over 100 hours of use.

Battery holder:  Radio Shack #270-396 battery holder.  This holder provides the internal connections between batteries and positive and negative output leads. Cost: $1.79

Switch connector jack:  Radio Shack #274-251 1/8? mono phono jack. Cost: $3.99 for package of 3

Pump:  American Science and Surplus (www.sciplus.com)  catalog # 36715 1200 cc/min pump.  Size ? 1 ? x 1 ? x 11/16?, outlet has 1/8? OD.  Requires 6 V @ 100 ma.  Cost: $14.75

Miscellaneous:  4 aluminum pop rivets, 1/8? dia. X 1/4? long, 4 washers for same, 4? of automotive vacuum hose approximately ?? OD, 1/8? ID., one 10-32 machine screw, 3/8? long and flat and toothed locking washers for same.  Soft foam pad, 1/2? thick to cover batteries.

Construction details:  

Figure 1 shows the internal construction of the balloon inflation device assembly.  All parts with the exception of the nozzle are packaged within the plastic enclosure.  The battery holder must be adjacent to one of the side walls of the enclosure so there is room to place the pump on the opposite side.  Unfortunately the cover mounting posts located in the two corners associated with that side wall interfere with locating the battery holder as desired and the lower section of these mounts must be removed to slide the battery holder beneath the remaining part of the cover mounts.  The unwanted parts were removed by cutting with a hot blade but could also be mechanically removed.  The remaining part of these two cover mounts remain attached to the case by a flange, but are relatively weak.  Consequently these were bonded to the corners using plastic plumbing pipe adhesive along with pieces of the removed plastic to fill the void.

The battery holder is provided with two mounting holes at each end.  With the battery holder located as desired, the four mounting holes were bored through the case and pop rivets inserted from the outside of the case.  Washers were placed over the end of the pop rivets in the battery holder prior to clinching the rivets. (See Figure 2)

Further prepare the enclosure by boring two 1/8? holes on each side to permit inlet air for the pump to enter.  Using Figure 1, determine a location for the switch jack and bore a hole with 15/16? OD to mount this jack.  Referring to Figure 3,  drill the box cover with an entrance hole for the rubber air tube and a mounting hole for the nozzle.  The nozzle can be immediately mounted to the cover using the 3/8? x 10-32 machine screw with a flat washer and a toothed washer under the head.

It is easiest to make the electrical connections to the various items prior to mounting them to the box (with the exception of the battery holder).  Those connections are:  Solder the negative (black) lead from the battery holder to the negative (unmarked) terminal of the pump motor after cutting the lead to a convenient length.  Solder the positive (red) lead from the battery to one terminal of the jack.  Solder a wire to the other terminal of the jack and connect the other end of this wire to the positive (marked with a red dot) terminal of the motor.

The pump is located in the area between the battery holder and the side of the enclosure, approximately mid-way between the ends of the case.  Attach the piece of vacuum tube to the outlet of the pump, make the electrical connections and then place a piece of double-sided foam mounting tape on the flat bottom of the pump.  After removing the protective cover from the second side of the tape, the assembly is pressed into the case to make the tape adhere.  The pump should be located so there is about equal clearance between each side of the pump and the surrounding structures.  Route the rubber tube beneath the mounting hole for the jack, then secure the jack in its mounting hole. When this is done the rubber tube can be trimmed to a desirable length and routed through the loose cover and secured to the nozzle port.

There is enough clearance between the tops of the batteries and the case cover that it might be possible for the batteries to partially pop out of the holder on impact.  So it is recommended that this space be filled by covering the battery area with a foam pad about 1/2? thick.

Finally, mount the cover with the screws provided with the enclosure.  If the torque required to drive the screws seems excessive you may want to bore out the mounting holes a bit.

The completed assembly is shown in Figure 4 with a balloon partially inflated.  For test purposes the pump can be operated by inserting a conductor having an OD of about 1/8? into the jack to complete the electrical circuit.  Note that the o-ring at the end of the neck is nested in one of the serrations of the nozzle to hold it.  Because the pump is very small the rate of inflation is quite slow, in the order of 2 to 4 minutes depending on how large the balloon is to be.  Although one may wish for a faster inflation rate, at least there is little danger of the balloon becoming over inflated and popping before the pump can be turned off.

Finally there is some buzzing noise while the pump is running.  This can be diminished by setting the case on a soft material like carpeting or a soft pad.

RCRV designer is Russell Schuchmann, and was requested by Prairie Crest Elementary, College Community Schools, Katie Thompson, 848-5280, Cell, 573-5100. The project was begun Oct 25, 2006 and completed Oct 25, 2006.

                   


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