Abstract: An electronic ballast circuit for fluorescent or other gaseous discharge lamps includes a resonant half-bridge inverter circuit. The source voltage to the inverter is a full-wave rectified line voltage together with a DC carry-over voltage for supplying power in the inter-cusp period of the recitified line voltage. A negative feedback circuit is responsive to lamp current to vary the inverter drive frequency and thereby regulate lamp current. The frequency response of the feedback loop is high enough and the gain-versus-frequency response of the inverter is such that lamp current and voltage are regulated to reduce the crest factor of lamp current to compensate for variation in the amplitude of the voltage across the semi-conductor switches.

Abstract: A paint roller guard assembly includes a paint shield adapted to support a paint roller, and a separate handle having a solid threaded mounting end which is received in a threaded connector portion of a cover mounted on a side wall of the paint shield to attach the handle to the paint shield during use of the paint guard assembly for painting. The handle is removable from the paint shield to permit a water hose to be connected to the connector portion to supply water under pressure to an inner chamber defined by the cover for discharge through apertures formed through the side wall of the paint shield to impact the paint roller causing it to rotate and simultaneously wash residual paint from the paint roller.

Abstract: Pull lines are utilized for installing electric wires in electrical conduit between junction boxes by attaching a pull line to the near end of a hollow-core line carrier having its forward end closed by a collapsible bag-like member of highly flexible plastic film or fabric. The bag-like member has a cross-section greater than that of the conduit and is inflatable through the trailing end of the line carrier so to maintain a yieldable continuous contact with the conduit interior wall about the line carrier as the carrier is moved through the conduit in response to a pressure differential created at one end of the conduit. In one form, the line carrier is a tubular sleeve of rigid or shape retaining material to which the pull line to be installed is attached; and, in a second form, it is a roll of the line itself which is disposed within the open end of the bag-like member. In a modification of the first form, the bag-like member is collapsed for storage within the sleeve.

Abstract: A paint roller guard assembly includes a paint shield adapted to support a paint roller, and a separate handle having a solid threaded mounting end which is received in a threaded connector formed on a side wall of the paint shield to attach the handle to the paint shield during use of the paint guard assembly for painting. The handle is removable from the paint shield to permit a water hose to be connected to the paint shield to supply water under pressure which is discharged through an elongated slot formed through the side wall of the paint shield to impact the paint roller causing it to rotate and simultaneously wash residual paint from the paint roller.

Abstract: A multi-position pressure relief valve settable to operate at different pressure limits includes an adjustment rod, a valve bias spring and a valve member extending coaxially with one another, the axial spacing between the rod and the valve member determining the pressure limit for the valve. The rod carries a pin adapted to engage a stepped surface of a limit select member, the steps defining a plurality of stop positions for the rod, and each stop position corresponding to a different pressure limit setting. A control knob attached to the rod enables the rod to be manipulated to locate the pin in the stop position corresponding to the pressure limit desired.

Abstract: An apparatus for facilitating field installation of electrical conduit and fiber optic lines in a conduit and a method of providing pull line in such apparatus.A roll of wound conduit tubing having a length of over 700 feet is provided with a pull line extending through the entire length of the wound tubing. The pull line has a tensile strength of about 45 pounds such that it will have sufficient strength to accomplish field pulling operations.

Abstract: A thyristor/capacitor inverter bridge energizes the lamp circuit with a high frequency oscillating voltage derived from full-wave rectified line voltage. Lamp current is regulated by a commutation circuit which is synchronized with zero crossings of the thyristor current. When power is first applied, an initialization circuit initiates a time delay to permit lamp warm up and then enables the high frequency inverter to begin energizing the lamp load. A re-strike circuit generates pulses coupled to the commutation circuit to re-start it when the rectified line voltage falls below that which is necessary to sustain oscillation of the inverter. Fault detection circuits are included for detecting faults such as loss of primary power, thyristor over-voltage, and thyristor over-current for taking corrective action, such as inhibiting the inverter and commencing a new initialization sequence.

Abstract: A fault protection system for a balanced thyristor capacitor/inverter half-bridge which generates a high frequency oscillating voltage from full-wave rectified line voltage is disclosed. Following the detection of thyristor over-current and the removal of transformer-coupled, alternating, gated drive signals from the thyristors by means of logic and control circuitry, the natural ringing of a charged resonant circuit coupled across the inverter half-bridge causes thyristor commutation and inverter shutdown. The resonant circuit and inverter half-bridge are isolated from the line voltage source during the fault recovery cycle by means of an inductance, the size of which is selected to greatly exceed the total inductance in the inverter bridge-resonant circuit system to avoid saturation until the power thyristors have been given sufficient time to turn off.

Abstract: A system for controlling the current in a solid state, high frequency ballast energizing a gaseous discharge lamp for providing light dimming therein is disclosed. The ballast includes a thyristor/capacitor inverter bridge for generating the lamp current which is regulated by a commutation circuit synchronized with zero crossings of the thyristor current. Lamp current and voltage level signals are fed back to the commutation circuit for proper lamp current regulation. A dimming signal is added to either the lamp current feedback or voltage feedback signal and this composite signal is provided to the lamp current regulator in varying the bias thereof for selectively controlling light intensity. Dimming may be accomplished either manually by means of a rotatable switch having an output which varies linearly with shaft rotation or automatically by means of an ambient light level sensor to provide a predetermined output light level which may be manually adjusted.

Abstract: Disclosed is a forced-air heat extractor for use in a conventional fireplace. The heat extractor includes a plenum through which air is circulated by means of a blower which is positioned in an inlet duct connected to the plenum and located in the fireplace. The plenum is provided with a temperature responsive relief closure in its top wall which opens to permit the free flow of heated air upward toward the fireplace's flue in the event the temperature in the plenum exceeds a predetermined value, as might occur in the event of an interruption in the flow of forced air through the plenum, thus protecting the blower motor and associated circuitry from excessive temperatures. A bottom bar having an air inlet to which is coupled the inlet duct is positioned on the forward, lower portion of the fireplace. Upon this bottom bar a firescreen may be conveniently positioned. An outlet duct similarly couples heated air in the plenum to an air outlet in the bottom bar.

Abstract: An air compressor has a low torque motor driven piston of the rocking rod type which operates in a cylinder with a closed head containing a discharge check valved port to a compressed air receiving chamber. The piston contains an intake port provided with a thin flexible metal spring closure strip which is inclined at a small angle to the valve seat about said intake port to open on the downstroke of the piston, close on the upstroke thereof and remain open when at rest to facilitate start and restart of the air compressor.

Abstract: A security alarm transmission system for protecting a building includes a plurality of alarm transmitter units each having a transmitter circuit controlled by associated condition sensors to generate coded alarm signals which are inductively coupled to a pick-up loop extending around the periphery of the building and extended to a receiver connected to the loop which decodes the alarm signals and provides a suitable alarm indication. The alarm transmitter unit is adaptable to provide different alarm outputs for indicating fire in the building or an unauthorized entry of the building, or an emergency condition, for example. The multipurpose alarm transmitter unit comprises a housing unit for containing the transmitter circuit, the housing permitting the transmitter circuit to be controlled by normally open or normally closed switches, and a mounting assembly which permits convenient installation of the transmitter unit at desired locations.

Abstract: The present invention is applicable to wobble piston compressors having overrun intake ports and being driven by a motor of low starting torque. In such a layout the vacuum created in the compression chamber upon initial motion of the piston from top standstill (at the outer end of the cylinder) may be great enough to stall the motor of low horsepower. The present invention provides an overrun relief port which, although it slightly lowers the overall efficiency of the unit, provides means for breaking the initial vacuum that tends to stall the motor on starting, and it provides that service, at a low cost, and with exceptional reliability. The loss in efficiency caused by the starting relief port, or ports, is minimized by locating the said port or ports at a point where the loss in efficiency on the compression upstroke is minimized. Small capacity air compressors of the rocking rod piston--wobble piston--type when driven by low powered A.C.

Abstract: The present invention provides a suspension lighting fixture utilizing a chain suspension for the lamp holder, and which fixture is attached at its upper end, mechanically and electrically, to an outlet box and to conductors mounted in the ceiling, respectively. The length of the suspension chain is adjustable without requiring cutting or parting of the same. The installation may be expeditiously and cheaply made and the structure involves a minimum of materials. The invention utilizes as an essential element a hanger which is adjustable relative to the individual links of the chain employed and through which hanger the swing canopy may be clamped against the ceiling by cooperating screw threads on said hanger and on the swing canopy.

Abstract: A small high speed direct connected motor compressor has a unitary piston and piston rod whereby the piston wobbles in the cylinder as the crank shaft rotates. The wobbling piston is sealed to the cylinder by a flanged disk of Teflon which forms both a seal and mechanical guide for the piston and which runs without lubrication in contact with a low-friction, surface-coated cylinder of high heat conductivity. The circular rim of the Teflon cup is warped from circular outline to elliptical outline twice per revolution while maintaining its seal with the walls of the cylinder. The structure involves small clearance spaces with consequent good efficiency.

Abstract: The invention provides an air compressor of low cost, high quality, long life and of simple and rugged construction and ready replaceability of the chief wear parts as a unit. The compressor employs a wobble piston with a Teflon or equivalent packing on the wobble piston, which packing bears against the surface of a working cylinder of aluminum with a hardened polished surface. The working cylinder in the form of a cylindrical sleeve is seated at its lower end on a circular shoulder in the main housing or frame. At its upper end it is seated and sealed in a groove in a head plate which provides a cylinder head for the cylinder and a closure for the top of the main frame. An inverted cup shaped delivery chamber rests upon and is secured to and sealed by an O-ring of heat resistant rubber to the head plate to receive the delivery of compressed gas and to provide anchorage for a delivery pipe or pipes.