Radio age research, manufacturing, communications, broadcasting, television (1941)

structure can be heated and the glue set. Materials that are good conduct- ors, such as metals, can be heated readily by radio frequency. When current flows in these materials, heat is generated by eddy currents and hysteresis loss. Thus by hold- ing a piece of metal in the field of the coil, power is absorbed and the material heats rapidly. This type of heating is generally referred to as the inductive method. Case hard- ening, soldering, brazing, melting and other operations are accom- plished readily by this method. The time required for a given soldering operation is greatly reduced since heat is actually induced in the part instead of being transferred from a hot iron or a gas flame. Individual soldering operations on terminals in transformer cans need not be done. By placing rings of solder under the terminals and placing the coil properly, soldering of all the termi- nals becomes a matter of seconds. Brazing operations can also be ac- complished by inductive heating. The coil is shaped to the area to be treated and the power is applied. The rate of temperature rise can be controlled quite accurately by the power used. The temperature can be brought up instantaneously or slowly, as desired. Most of us are familiar with the usual method of riveting, where one man drives the rivet while another man holds a tool against the end to flare it. This method has been used since the riveting process was de- veloped. It is satisfactory except in confined spaces where it is difficult to reach the other end of the rivet. One aircraft company even resorted to employment of midgets to work in confined spaces. Even so, wing tips and other places present diffi- cult problems. A skilled workman could rivet perhaps only one or two of the old-fashioned rivets in a minute simply because his helper could not manipulate the tools fast enough. The du Pont Company developed an ingenious explosive rivet which did not require a helper to get at the other end. This rivet has a heat-sensitive explosive charge in one end. When the charge is fired, it expands the end of the rivet, forming a perfect, barrel-shaped ELECTRONIC UNIT FOR SPOT GLUING, USING R.\DIO FREQUENCY. head that holds the two pieces of material firmly together. The ad- vantage of using this rivet in inac- cessible places is obvious. Almost anyone today can set 15 to 20 ex- plosive rivets in a minute as com- pared to the one or two by the old method. ELECTRONIC METHOD OF SOLDERING TERMINALS ON TRANSFORMER CANS. One method of firing explosive rivets is by means of a riveting iron which was developed specifi- cally for this purpose. It is similar in construction to a soldering iron and has a silver alloy tip which con- ducts the heat to the rivet head. This rivet firing tool has the disad- vantage that considerable time is required either to attain operating temperature or in changing from one tip temperature to another. In order to find a more satisfac- tory solution for firing the rivets, particularly in large scale produc- tion, RCA engineers, in cooperation with du Pont engineers, developed a radio-frequency rivet detonator. This unit consists of an oscillator together with a specially developed applicator to concentrate the cur- rent directly into the rivet head. As the current is induced into the rivet head, the rivet heats very rapidly and this heat fires the charge. This method has a number of advantages. Most important of all, better temperature control is obtained, since the power output control of the o.scillator can be quickly changed to suit the require- ments of the various sizes of rivets. A number of rivets can be put in place ahead of the riveter and held in place by scotch tape, since this tape does not interfere with the action of the radio frequency de- vice. The above are only a few of the possible applications. The solution of one problem always suggests the solution to another. Radiothermics is truly a time saver for industry. Short production cycles are always important, but never so important as today when material is so badly needed by the United Nations. RCA is also serving by helping others save precious hours. •■News for Mexico." a daily series of ten-minute Spanish newscasts provided for the exclusive use of station XEW and its 41 affiliated stations in Mexico, is being trans- mitted daily over RCA Communica- tions, Inc., facilitie.-;. The Mexican outlets are affiliated with NBC's Pan .American network. PLYWOOD CLUB USED FOR TESTING AIR- PLANE MOTORS IS SHOWN UNDER RADIO FREQUENCY HEAT TREATMENT.