Abstract: Method and apparatus for in vivo or in vitro selective deposition of microwave power patterns in lossy dielectric materials, particularly biological tissue. Configured as a needle-like probe, a miniature coaxial cable (1) having a circumferential gap (12) in the shield (2) is wrapped with an electrically thin dielectric substrate (18). The cable center conductor (6) extends immediately past gap (12) and is shorted to cable shield (2). A thin conductive dipole resonator (21) is positioned on substrate (18) and over gap (12) to achieve inductive coupling between the cable center conductor (6) and the dipole resonator (21) through gap (12). The ends of the dipole resonator (21) are capacitively (22) loaded so as to make the current on resonator (37) more uniform and to greatly reduce and stabilize the resonant frequency to be essentially insensitive to the dielectric properties of the surrounding material.

Abstract: A plasma processing apparatus and method using a predetermined proportion of relative power between a TE.sub.11 mode and a TM.sub.01 mode to produce radial uniformity of the plasma. A microwave coupler transforms microwave energy from a microwave source into approximately equal proportions of TE.sub.11 and TM.sub.01 modes. In one embodiment, the coupler includes a first arm for generating the TE.sub.11 mode and a second arm for generating the TM.sub.01 mode which are then combined in a cylindrical waveguide section having a sufficient inner diameter to support propagation of both modes. Other circuit components are provided to prevent cross-coupling of the TE.sub.11 mode into the TM.sub.01 generating arm, and vice versa. Thus, the relative proportion of power of each mode may be independently controlled. A magnetic field generator may be used in the apparatus to create an electron cyclotron resonance condition within the plasma.

Abstract: A safety system for a machine tool, e.g. an EDM machine, having a multiplicity of different items of setting procedure to be attended to manually and inspected by the operator before the machine is actuated for performing a given machining operation, employs a loudspeaker associated with the machine. A control unit is used to produce a preselected sequence of multiple, time-spaced electrical signals corresponding to multiple verbal instructions prescribed for alerting the different setting items, respectively, and to apply these signals in that sequence to an electromechanical transducer in the loudspeaker. The transducer responsive to each of the electrical signals produces through the loudspeaker a corresponding unit of the multiple verbal instructions audible to the operator for a corresponding item of the setting procedure.

Abstract: Servo control circuits particularly suited for electric discharge machining apparatus to provide the input to the servomechanism which actuates the tool feed during machining.These circuits respond to a setting of desired gap emf and an input of actual gap emf to control tool movement so as to equalize these inputs. They respond to abnormally low gap emf during the machining "on" pulse to retract the tool to allow the gap to clear of debris.The gap emf during the "on" period of the pulse cycle is stored in a small capacitor coupled to a high-impedance input to power circuits of the servo control, which capacitor normally retains most of its charge during the "off" time of the cycle. Logic circuits responding to the pulse generator and the gap emf discharge this capacitor when abnormally low gap emf occurs during cycle "on" time.

Abstract: Some forms of EDM employ monitoring of sparking in the gap between an electrode and a workpiece to control the machining process but difficulties arise in providing a threshold which when applied to the monitoring signal indicates the onset of arcing. This problem has been found to be due to the change in amplitude which occurs with gap current in monitoring signals derived in some ways. The invention uses a threshold control circuit to provide a variable reference signal for a comparator which compares the monitoring and reference signals, the magnitude of the reference signal varying inversely with the gap current. The output of the comparator determines by way of a drive circuit and transistors whether or not voltage is applied between an electrode and a workpiece.

Abstract: A process and apparatus for increasing the frequency of the effective machining electrical discharges between the electrode workpiece and the electrode tool of an EDM apparatus. The process of the invention consists in monitoring the electrical parameters in the machining zone between the electrodes such as to detect short circuits, and, when a short circuit is detected, in continuing monitoring the electrical parameters until monitoring indicates the disappearance of the short circuit, in cutting off the ongoing electrical discharge after a predetermined time interval following the moment at which said short circuit disappears and in re-establishing normal electrical voltage pulses after another time interval following the end of the discharge. The invention also provides appropriate apparatus for practicing the process.