|Food Chain No. 21 - July 1997 (ITDG, 1997, 20 p.)|
A LOCALLY DESIGNED IMPULSE HEAT SEALER
Food Chain's technical advisor was recently in Ghana where he met John Kojo Arthur who has worked at the University of Science and Technology in Kumasi. John, an electrician, has designed and built a very clever, simple heat sealer.
He made the first unit in 1979 for his wife who was setting up a small enterprise making polythene hags from rolls of film. She now has three machines, two basic ones for cutting the film into sheets and one with an electronic timer for making the bags. The finished bags are sold to traders in local markets.
John has developed two models based on the basic design. The cheaper of these which sells for $US75 has no built in timer, the user simply controls the sealing time by experience. A model with a built in 0.5 to 5 second electronic timer sells for $US175. If sealing thicker, high-density poly-ethelene (HDPE), a poly-tetra-flueroe-thylene (PTFE) cover strip is used over the heated sealing wire. However, no PTFE cover strip is used if only thin, low density poly-ethylene (LDPE) is to he sealed. To date John has sold one electronic machine and over 50 basic models.
As can he seen in the photograph the sealers are operated by foot, leaving troth hands free to handle the film. The bottom jaw" of the sealer containing the heated wire sealing strip is mounted on the work table. Depressing the foot pedal causes the rectangular steel frame to move downwards bringing the upper sealing head, mounted on the base of the moving frame, into contact with the bottom sealer. tom sealer.
At this point a pin pushes against a simple push switch so allowing current to flow and heat the sealing element. The work table is marked so that bags of different sizes can be made.
A locally wound mains transformer supplies 24 volts to the sealing wire. John makes his own strips of sealing wire by straightening spiral wound elements from electric cooker elements that are available in local markets.
John explained some of his problems. The most serious is that the fine heating element wire only produces a very narrow, and thus weak, seal. By chance, our advisor had some 3mm wide heat sealer strips with him and these were given to John so that he could test them. If they work he will be able to import more. He feels that there is a growing market for heat sealers and in particular expects the demand for the electronically timed model to increase. The cost of the timer which has to he imported is a problem. He has a circuit diagram for such a timer and we have agreed to assist him source the components so that a cheaper timer can be made in Ghana.
A HAND OPERATED CASHEW CRACKER
In many countries cashew nuts are processed by small enterprises and find a market as a popular snack. The nuts have to be removed from the outer shell which contains a very unpleasant, corrosive liquid. Hand cracking, often using stones or wooden mallets is a very undesirable task. Kaddai Engineering in Ghana has designed a simple, low cost cracker which work. very well. Although, as can be seen in the illustration, the machine is simple, Kaddai have given considerable attention to the design of the critical component - the blades that split the outer shell without breaking the nut inside.
For further details contact Kaddai Eng., PO 2268, Kumasi, Ghana