Abstract: A constant voltage power supply employs a circuit in which the average voltage over a specified period of time is maintained constant by a circuit for charging a voltage storage means with width modulated pulses applied several times during each specified period whereby to charge the storage means above the desired average level and terminating charging until the voltage falls below the specified level. The period of time over which the voltage is averaged is a function of the thermal inertia of a load to be driven. The average voltage is employed as the energizing circuit to a high frequency oscillator, and driver stages supplying the output of the oscillator to an output stage of a power supply whereby the energizing voltage of the stages and thus the dissipation of energy therein does not exceed that required to feed the lead at its then current energy requirements.

Abstract: An autoregulating electrically shielded heater employs a structure of two magnetically permeable members of different Curie temperatures and preferably differing resistivities. The two members are in electrical contact with one another; having at their interface a very low resistivity layer or member provided by copper or a like material. A first of the electromagnetic members has the lower Curie temperature and high resistivity while the other of said members has the higher Curie temperature of the two and preferably lower resistivity. A constant current a.c. source is connected to induce currents in the members parallel to their interface. Below the Curie temperature of the first member, current is substantially confined to a narrow region along a surface remote from the interface. Above the Curie temperature, some of the current spreads into the low resistance layer or member and into the second electromagnetic member where it is confined, due to skin effect to a narrow region adjacent the interface.

Abstract: The impedance of an autoregulating heater is greatly increased by employing in one embodiment a return conductor in the form of a helix surrounded by and insulated from a magnetic conductor; the two conductors connected in series or as a transformer across an a.c. source whereby the current in the magnetic material is forced to follow a helical path. In a preferred embodiment, a multilayered coil is wrapped about and insulated from a magnetic sleeve disposed about a copper rod; the sleeve and rod forming the secondary of a transformer. The helical path of the current in the secondary plus the impedance transformation effect of the transformer greatly enhances the impedance of the load as presented to a current source. The winding is enclosed within another magnetic sleeve which provides another magnetic shield about the heater and if connected at one end to the inner magnetic layer increases the width to thickness ratio for purposes to be described.

Abstract: Designation of specific heating zones and increase in minimum resistance relative to prior heaters of the type to which the present invention pertains is achieved, together with flexibility or bendability, if desired, by slotting the outer conductor of the heater. Additional flexibility is also achieved by confining the high mu material only to those regions of the device where heating is desired, the unslotted regions.

Abstract: A heating structure is described having both a return conductor and a heating element consisting of a substrate of a non-magnetic material having high thermal and electrical conductivity, clad with a surface layer of a ferromagnetic material of relatively low electrical conductivity.

Abstract: A flexible autoregulating heater with a latching mechanism to form the strap that may be applied about work to be heated, the strap holding the work during the heating and subsequent cooling cycle. The strap may then be removed or permitted to remain in place to provide a resulting binding force about the finished product. A band strapping tool is modified to not only draw the strap tight but apply electric current to activate the heater.

Abstract: An autoregulating, electrically shielded heater employs a laminated structure having two magnetic alloy permeable materials of widely differing Curie point temperatures and preferably of differing resistivities. A constant current supply is connected across the laminate such that current flows in the laminae along parallel paths. Due to skin effect, the current is confined to a thin region of a first lamina which is located between the other lamina and the electrical return path. This first lamina has the lower Curie temperature and preferably the higher resistivity of the two laminae to produce heating proportional to I.sup.2 R.sub.1. When the Curie temperature of the first lamina is approached, the current spreads into the other lamina which may have a lower resistivity and higher Curie temperature and heating is obtained by I.sup.2 R.sub.2 where I.sup.2 is a constant due to the constant current source and preferably R.sub.2 <R.sub.1.

Abstract: The lid is hermetically sealed to an associated box by a gasket in the form of a sealant covered temperature autoregulating heater.

Abstract: A simple, highly flexible, virtually massless, temperature autoregulating heater primarily useful for soldering has an energizing circuit that may be integral with or separate from the heater element, which element has a ferromagnetic material energized via the circuit from a constant current source whereby regulation occurs about the Curie temperature of the magnetic material. The energizing circuit may be in the form of a printed circuit conductor formed on a thin layer of Kaptan or like high temperature insulating material having the heater formed on the reverse side thereof or having a sticky substance thereon so that the energizing circuit may be temporarily adhered to the heater and removed after use. Alternatively, the energizing circuit may be formed directly on Nomex paper or the like; a quite thin paper with a sticky backing.

Abstract: The present invention achieves constant voltage at radio frequencies to drive a constant voltage to constant current converter, by employing a tightly coupled d.c. feedback loop to control the voltage via a transformer to the drain of a FET operated as a Class C amplifier in the saturated mode whereby among other advantages, the amplifier can withstand, without damage, very high VSWRs. Control is affected by a high gain differential amplifier which compares a d.c. voltage derived from the r.f. output of the system against a highly stable d.c. voltage reference. A controller, responding to the output of the differential amplifier causes a first level of voltage to be applied to the drain of the FET when the system is not loaded and causes a second voltage varying between said first level and a higher level when the system is loaded.

Abstract: Apparatus and process for selectively heat treating at least a portion of an article in the field with autoregulated heating. The autoregulated heating is provided by a heater including at least a first magnetic material disposed along the portion of the article to be heat treated. The first magnetic material has a magnetic permeability which sharply changes at temperatures at or near the autoregulating (AR) temperature thereof. The changes in permeability result in corresponding changes in the skin depth of the first magnetic material and, hence, the heating produced therein responsive to a.c. current passing therethrough. By maintaining the a.c. current constant in amplitude and frequency, the first magnetic material and the portion of the article are regulated at substantially the AR temperature of the first magnetic material.