Abstract: A conformal skate for use in an inductive welding system for creating a fusion bond along a bond line between two thermoplastic parts includes a wheel having a circumferential casing made of fluid impervious flexible material. The wheel is rotatably mounted on a fixed axle by fluid tight bearings. The axle has an axial passage for admission of pressurizing and cooling fluid, and for power leads for the coil and for leads for sensors inside the wheel. A vertical mount on the axle supports the coil for vertical motion and biases the coil downwardly so that it remains in contact with the inside surface of the casing despite unevenness or contour changes in the upper surface of the top part or changes in the wheel shape when the fluid pressure in the wheel or downward force on the axel is changed.

Abstract: A fixed coil induction heater produces quality thermoplastic fusion welds in prefabricated resin composite parts. A susceptor along a bondline between parts aligns with the induction coil segments of a solenoid induction coil along the centerline of the coil. Energizing the coil heats the susceptor to form the weld at the bondline. For this operation, our induction heating workcell uses complementary dies that define a central cavity with an oval pattern of induction coil segments roughly conforming to the shape of the cavity and surrounding all faces of the cavity where we position the preform composite parts and susceptor.

Abstract: Susceptors for induction heating for use in thermoplastic welding are tailored to provide precise control of the heat applied to the weld and especially to control overheating at the edges of susceptor. The preferred susceptor has a central portion having a uniform pattern of substantially similar openings and selvage edge strips devoid of openings to provide a low impedance current path for eddy currents at the edges. We can create aerospace structure, particularly a wingskin-spar assembly, without fasteners.

Abstract: To obtain more uniform heating across the susceptor when welding composite parts using induction heating, we create edge regions of lower absolute impedance or a lower longitudinal impedance than the transverse impedance to counterbalance the higher current density and current that occurs near the edges. We achieve lower impedance at the edges by altering the aspect ratio (length/width) of openings in the susceptor, by folding the susceptor over onto itself, or both. Uniform heating is important to obtaining a uniform, consistent weld on which aerospace designers can rely.

Abstract: An asymmetric coil which has an "A" winding on one pole of the "C" core and a "B" winding of opposite helical twist, on the other pole, we can achieve relatively uniform, intense heating between the poles with relatively insignificant heating outside the poles. Only one core winding is active at one time. This coil allows us to heat uniformly to the ends of the susceptors on the ribs without remelting or overheating the welded area under the abutting spar, as FIG. 6 illustrates. The asymmetry provided by the two windings of opposite helical sense and the core design allows us to travel in either direction by activating the appropriate coil.

Abstract: A method of riveting includes drilling a hole in a workpiece with a drill bit held in a spindle mounted on an axial centerline of a drill/rivet machine. The drill descends through a drill/suction cavity of a movable shuttle and drill chips cut by the drill bit are suctioned away from the workpiece as they are made. The drill bit is withdrawn to a level just above the drill/suction cavity, which is then moved to position a rivet insert station over the newly drilled hole in the workpiece. A rivet is blown into the rivet insert station, is guided into alignment with the hole and injected directly into the hole by air pressure. The shuttle moves a rivet die over the newly installed rivet in the hole and a driver of an electromagnetic riveter is lowered into contact with the die, which in turn is pressed against the rivet head. Another rivet die is pressed against the rivet tail on the other side of the panel by a driver of another electromagnetic riveter.

Abstract: There is disclosed a high power induction heating coil for use in thermoplastic welding where a metallic susceptor is imbedded in a composite assembly and is heated by eddy currents generated by the coil. The coil is comprised of several windings of Litz wire composed of multiple individually insulated strands of copper wire. The coil is wound on a circular E core having a coolant conduit through the center of the core. Coolant is introduced through the central core and returned by circulating through the loosely wound coil to the coolant source.

Abstract: This invention relates to a machine and its constituent components for drilling a hole in a workpiece, inserting a rivet in the hole, and upsetting the rivet, all without moving the lateral position of the machine or the workpiece, and to an assembly for supporting and positioning a plurality of said machines for working simultaneously on the workpiece.

Abstract: A method of detecting an effluent level in an aircraft lavatory holding tank and a device for practicing the method. The device uses electrodynamic forces of different values generated by an electro-impulse solenoid to determine whether a detector is contaminated, to dislodge contaminants, and to measure the fluid level in the holding tank when the detector is clean enough to produce an accurate reading.

Abstract: An electromagnetic dent remover having a tapped work coil (36) is provided. A first current pulse, I.sub.S, is applied to an inner and outer coil (48 and 46) to produce an electromagnetic field that exerts a repelling force on a conductive part (24). A second current pulse, I.sub.F, having a polarity opposite that of the I.sub.S current pulse and a rise time shorter than that of the I.sub.S pulse, is applied to the inner coil (48), which collapses the electromagnetic field associated with the inner coil (48) and causes a pulling force to be exerted on the part (24) by the inner coil (48). The work coil (36) is positioned over a dent in the conductive part (24) so that the pulling force produced by the inner coil (48) is concentrated on the dent and pulls the dent from the part (24). Simultaneously, the pulling force is counteracted by the repelling force produced with the outer coil (46). The repelling force stabilizes the part ( 24) to facilitate the removal of the dent.

Abstract: Disclosed is an eddy current inspection system for nondestructive detection of subsurface flaws in regions of multilayer conductive structure that surround a fastener which joins the conductive layers. The eddy currents are induced by an aperiodic drive current having a relatively long rise time and a relatively last fall time that is supplied to a drive coil and a pick-up coil that is mounted with the drive coil supplies a signal representative of the induced eddy currents. Compensation is provided for variation in lift-off (spacing between the surface of the structure being inspected and the surface of the drive coil and pick-up) by utilizing parametric relationships relative to the maximum amplitude of inspection signals supplied when subsurface flaws exist and inspection signals supplied when lift-off is present.

Abstract: Nondestructive evaluation of conductive materials is disclosed wherein a magnetic field having a relatively slow rise time and a relatively fast fall time induces eddy currents in the conductive material being tested and subsurface flaws such as internal cracks or other discontinuities are detected by monitoring the magnetic field produced by the eddy currents. The magnetic field is generated by sequentially discharging two capacitor banks through a coil with the currents supplied by the capacitor banks being of opposite polarity and the first capacitive discharge exhibiting a time constant that is substantially longer than the second capacitive discharge. The initial, slowly rising portion of the magnetic field establishes magnetic flux that extends to substantial depths within the conductive material and the fast fall time of the magnetic field causes eddy currents of substantial magnitude to circulate within the region of the conductive material being examined.

Abstract: An electromagnetic force (EMF) machine with a universal portable power supply is disclosed. The universal portable power supply energizes either a multiple turn flux concentrator or a single turn flux concentrator. The flux concentrators produce magnetic fields that create an outward tension force adapted to perform non-destructive bond tests (tension proof loading) and/or dent removal operations on panels or the like. The power supply includes a slow current pulse subsystem; a fast current pulse subsystem; slow and fast crowbars; and, a firing control. The firing control controls the production of pulses by the slow and a fast current pulse subsystems, and, the operation of the slow and fast crowbars. The slow pulse subsystem, via the flux concentrator, slowly creates a magnetic field that penetrates the panel; the fast pulse subsystem, via the flux concentrator, rapidly decreases the magnetic field, whereby a negative field gradient is produced across the panel.

Abstract: An adjustable regulator and a cycle initiating firing pin are mounted in the handle of a casing which contains a flux concentrator. The adjustable regulator sets the amplitude of current from a control panel to the flux concentrator through a flexible multi-conductor cable. The flux concentrator is separately encased and detachably mounted to the casing.

Abstract: An electromagnetic dent remover including a dent removal head containing an electromagnetic work coil capable of creating a locally concentrated magnetic field when first energized by a slow rising current followed by a fast pulsing counter current is disclosed. The electromagnetic work coil comprises a cylinder formed of a spirally wound metal strip whose convolutions are electrically insulated from one another by coatings or layers of electrical insulation. In one form, slots and holes, located in the walls of the coil, control the electrical current density within the coil to thereby produce the desired locally concentrated magnetic field. In another form, the ends of the coils are machined such that at least one magnetic field concentration projection projects outwardly from one annular end of the coil. The other end of the coil is machined such that it is a mirror image of the projection end.

Abstract: A flux concentrator has a pair of primary coils wrapped around a thin walled cylindrical portion of a secondary coil. The secondary coil has a conductive head at an end and the coil is slotted to generate a rapid high intensity axially acting flux at the head in response to a flow of current through the primary coils. A pulling force is generated as a result of a slow rise high amplitude current flow through one of the coils followed by a rapid rise reversed polarity current flow through the second primary coil.

Abstract: An electromagnetic dent remover including a dent removal head containing an electromagnetic work coil capable of creating a locally concentrated magnetic field when first energized by a slow rising current followed by a fast pulsing counter current is disclosed. The electromagnetic work coil comprises a cylinder formed of a spirally wound metal strip whose convolutions are electrically insulated from one another by coatings or layers of electrical insulation. In one form, slots and holes, located in the walls of the coil, control the electrical current density within the coil to thereby produce the desired locally concentrated magnetic field. In another form, the ends of the coil are machined such that at least one magnetic field concentration projection projects outwardly from one annular end of the coil. The other end of the coil is machined such that it is a mirror image of the projection end.

Abstract: An apparatus and method of electromagnetically pulling dents from conductive material. A coil is formed to direct an effective electromagnetic coupling to a limited area between the coil and a dented part. A nonconductive mold placed between the coil and part has openings to overlie the dent. The coil is first energized with a slowly rising current then is energized with a fast pulsing countercurrent to generate a strong pulling electromagnetic coupling.