Abstract:
A power supply (80) for an electrostatic spray gun (70) includes a circuit for dynamic manipulation of an operational loadline. Various embodiments are provided, including an analog circuit, a variable frequency circuit, a variable waveform circuit and a variable impedance circuit. The manipulation circuit may be used with either or both of an internal and an external feedback arrangement.
Abstract:
A high voltage generator is provided for use in applications where current demand is low but a high voltage is required. The generator comprises an array of photosensitive elements, such as an array of photovoltaic elements produced by laser scribing or etching of a wafer of material conventionally used for solar cells, the number of elements employed and their interconnection being such that a high voltage output of at least 1 kV is obtained.
Abstract:
A method and device for monitoring the production of a high voltage for use in electrostatic application of a coating product, the high voltage being produced by a generator and the monitoring being performed by a circuit for measuring an electrical parameter associated with the high voltage, together with verifying operation of the circuit immediately following start-ups of the generator.
Abstract:
A rotary atomizer has an internal power supply in the atomizer housing about which is passed cooling air. The air then flows out of the atomizer housing in a twisting direction as vectored air in the same direction of rotation as the atomizer head to eliminate any vacuum condition around the atomizer head and to provide shaping control of the coating being sprayed. Exhaust air from an air turbine motor driving the atomizer head is directed around the outside surface of the atomizer housing to prevent the liquid coating from wrapping back and accumulating onto the atomizer housing. A speed sensing system is mounted in the atomizer housing and utilizes both magnetics and optics for accurately measuring the rotational speed of the air turbine motor in the presence of high electrostatic charge and RF fields from the internal power supply. The power supply is disposed within the atomizer housing about the turbine motor. The atomizing head, in one embodiment, incorporates an insert which divides the flow of coating material into a plurality of individual streams to improve the atomization of the coating material from the atomizing head. In another embodiment, an insert is located in the atomizing head to insure that the front flow surface of the atomizer head remains wet during operation so that the atomizing head is easier to clean. The power supply is ring shaped and encircles the turbine and the paint flow passage through the turbine. An intrinsic safety barrier is provided to supply electrical power to the power supply. The intrinsic safety barrier is incorporated into the feedback loop of a voltage regulator.
Abstract:
The invention provides a method of generating a high voltage in an electrostatic powder coating gun with a high-voltage generator having a transformer and a high-voltage cascade arrangement. The primary coil of the transformer is fed with an a.c. supply voltage operating at a working frequency. During operation of the coating gun, the frequency of the supply voltage is continuously varied about the working frequency, the current intensity of the primary coil current of the transformer is also continuously detected and the direction of frequency variation is reversed every time an increase in the current intensity of the primary coil current is determined. An electrostatic powder coating gun operating with the present high-voltage generating method includes a current detection circuit for continuously detecting the current intensity of the primary coil current of the transformer, a sweep generator for continuously varying the frequency of the supply voltage about the working frequency, and a control for controlling the operation of the sweep generator.
Abstract:
Induction charging apparatus for HVLP spray guns includes an air cap having a central fluid exit orifice for receiving the spray gun nozzle. The cap includes one or more charging electrodes surrounding the orifice and carrying a voltage sufficiently large to induce on the spray droplets charges of a polarity opposite to that on the electrodes. The cap includes a rotatable electrical connector to enable the cap to rotate 360.degree., while maintaining electrical connections between the electrodes and a power supply.
Abstract:
An apparatus is provided for transferring electrically conductive coating materials, such as water-based paint, from at least one source to one or more coating dispensers for discharge onto a substrate. One voltage block is provided to avoid the creation of an electrical path between one or more sources of coating material and the coating material which is electrostatically charged during a coating operation, and a secondary voltage block is provided between each of a number of individual spray guns and the charged coating material so that each spray gun can be electrically isolated from the charged coating material when not is use. The apparatus is optionally provided with a color changer, and/or a heater which is electrically isolated from the charged coating material and is effective to elevate the temperature of the coating material prior to discharge from the spray guns.
Abstract:
An apparatus is disclosed suitable for electrostatic spraying from fixed wing aircraft. The apparatus includes a linear electrostatic spraying nozzle 2 and electrodes 4 placed near the nozzle's spraying edge to intensify the electric field strength at the spraying edge sufficiently to produce ligaments of the liquid to be sprayed from the spraying edge. In order that the airstream due to the aircraft's movement does not destroy the ligamets, the sprayhead and the electrodes are positioned so that part of the airstream flows between them. The spray head and the electrodes are so shaped and positioned that when directed to spray in substantially the same direction as the airstream, a turbulence free wake is left in the region of the ligaments.
Abstract:
A spray-coating device for spraying liquid or powdered coating material on articles includes a transformer for stepping up an alternating voltage and a voltage multiplier circuit for converting the output of the transformer to a high DC output for driving a charging electrode in the spray-coating device. The alternating voltage for the transformer is obtained from a controllable source of alternating voltage which produces a sinusoidal voltage whose frequency is constantly adjusted such that the voltage and current flowing through the transformer are in phase with one another. This assures that the transformer is operated at its resonant frequency.
Abstract:
A high-voltage generator for electrostatic sprayer devices includes a frequency-clocked power amplifier for feeding the primary of a transformer whose secondary is connected to a high-voltage cascade or multiplier circuit. The power amplifier is connected to a controllable low-voltage d.c. voltage source and to a controllable frequency generator, whereby the control of the d.c. voltage source and of the frequency generator is provided by a microcomputer such that the transformer is optimally matched for all voltages appearing at the high-voltage output of the cascade.