Abstract: An electrical system which is part of a control system for a heat pump is disclosed. In addition to other functions, the electrical system protects an AC power supply for the control system from a short circuit condition in an electrical load connected to the power supply. The electrical system includes a device for monitoring the voltage drop across the load and for generating an electrical clock signal only when the monitored voltage drop exceeds a selected level indicating no short circuit condition in the load, a microcomputer having an internal timer for receiving any generated clock signal, and relay means controlled by the microcomputer for operating switches to disconnect the AC power supply from the load when a short circuit condition is detected in the load.

Abstract: A refrigerant expansion device for use in a vapor compression refrigeration system is disclosed. The device has a body portion with a bore extending therethrough. At least that portion of the body portion which forms the bore walls is made of a shape memory alloy which undergoes a metallurgical transformation at a predetermined transformation temperature to change the bore size of the device in response to the temperature of refrigerant flowing through the device. In this manner, the bore size of the device is adjusted in response to different operating conditions of the refrigeration system.

Abstract: An electrical control system for environmental conditioning equipment such as a heat pump is disclosed. An electronic control module in the control system has input and output plugs which may be disconnected from the module and connected to each other so that the module is bypassed while maintaining basic operation of the equipment. This allows the electronic control module to be serviced, tested, and/or repaired while maintaining basic operation of the equipment.

Abstract: Apparatus and method for forming fins on a tube surface. The apparatus comprises a plurality of roller assemblies and each roller assembly includes first and second spaced apart sets of discs. The first set of discs have progressively increasing outside diameters in a forward direction. The second set of discs includes a first subset of discs having outside diameters generally equal to the outside diameter of the forwardmost disc in the first set, and a second subset of discs having progressively increasing outside diameters in the forward direction, with the outside diameter of the forwardmost disc in the second subset generally equal to the outside diameter of the forwardmost disc in the first set.

Abstract: A method of making a new high performance heat transfer tube for use in an evaporator of a refrigeration system is disclosed. According to this novel method, a grooved mandrel is placed inside an unformed tube and a tool arbor having a tool gang thereon is rolled over the external surface of the tube. The unformed tube is pressed against the mandrel to form at least one internal rib on the interior of the tube. Simultaneously, at least one external fin convolution is formed on the exterior of the tube. The external fin convolution has depressed sections above the internal rib where the tube is forced into the grooves of the mandrel to form the rib. A smooth roller-like disc on the tool arbor is rolled over the external surface of the tube after the initial formation of the external fin and internal rib. The resulting heat transfer tube has an exterior with a subsurface channel consisting of interconnected cavities and subsurface passages.

Abstract: A strain isolation technique for a surface acoustic wave (SAW) device having a piezoelectric SAW substrate is disclosed. A cut in the surface of the piezoelectric SAW substrate forms an isolated surface region where active SAW signal propagation occurs. The cut prevents undesirable surface strains from affecting SAW signal propagation in the isolated region.

Abstract: A method of arc welding is disclosed. Specifically, a method of pulsed direct current (DC) arc welding is disclosed wherein special pulses of positive direct current are used to weld together work pieces. The special DC pulses are capable of dissipating difficult to reduce oxides which may be present on the surfaces of the work pieces without using a flux. The method is especially useful for fluxless arc welding of aluminum, particularly thin wall aluminum tubing used in making heat exchangers for air conditioning systems.

Abstract: A safety device is disclosed for detecting a flame rollout condition at the burners of a combustion system and for shutting down the system in response thereto. The invention consists of using sections of the insulated leads, which are used for transmitting power from a fuel supply control transformer to a fuel supply system of the combustion system, as a flame rollout condition safety means. The sections of the leads are positioned so that the insulation burns off the leads to create a short circuit causing the transformer to over-heat and burn out thereby closing a fuel supply valve of the fuel supply system when a flame rollout condition occurs.

Abstract: An alarm device for monitoring the movements of a person is disclosed. The device is designed to be attached to a person's clothing and is particularly suitable for use by an emergency worker, such as a fireman. The device comprises a motion sensor, a signal processing circuit on a printed circuit board, and an alarm, all contained within a housing. The motion sensor includes a permanent magnet attached to one end of a spring located within an induction coil wound on a bobbin. The other end of the spring is attached to the printed circuit board so that a voltage is induced across the coil due to vibrations of the magnet relative to the coil in response to movements of the housing of the device. The signal processing circuit activates the alarm to generate an alarm signal if the person is immobile, for example, as the result of an injury, for a predetermined period of time.

Abstract: A centrifugal vapor compressor and a method of assembling the same. The compressor comprises a housing defining an inlet passage and a diffuser passage, and an impeller blade rotatably mounted in the housing between the inlet and diffuser thereof. The compressor further comprises an annular recess defined by the housing and in communication with the diffuser passage, and an annular diffuser valve supported by the housing for axial movement within the annular recess and the diffuser passage between minimum and maximum throttling positions. A stop member is located adjacent to the housing and includes an end section axially located forward of the annular recess to limit forward axial movement of the diffuser valve. A fastening member is radially located external of the annular recess and disengagably secures the stop member to the housing.

Abstract: A device for detecting displacements of a fluid jet is disclosed. The device is particularly suitable for use as part of a fluidic angular rate sensor. The device comprises a wire resistor suspended between a pair of metal posts, a means for producing a magnetic field at the location of the resistor, an alternating current (AC) source electrically connected across the resistor for heating the resistor and for interacting with the magnetic field to cause the resistor to oscillate, and readout electronics for sensing changes in wire resistance which are a function of wire temperature variations associated with fluid jet displacements. The use of a single oscillatory wire resistor eliminates the need for the difficult to achieve and costly wire matching procedures of conventional two wire fluid jet displacement detectors.

Abstract: A method of regulating startup operation of a vapor compression refrigeration system to prevent oil pump cavitation during startup of the refrigeration system is disclosed. The method comprises monitoring the rate of decrease in evaporator pressure or temperature or monitoring compressor suction line pressure and then comparing this monitored rate to a rate of pressure or temperature decrease which is predetermined to prevent oil pump cavitation. If the monitored rate exceeds the predetermined rate control action is taken to adjust the capacity of the compressor to provide a desired rate of pressure drop which prevents oil pump cavitation. A microprocessor control system and a mechanical control system are disclosed for carrying out the disclosed method.

Abstract: A method and apparatus to prevent oil pump cavitation in a hermetically sealed vapor compression refrigeration system are disclosed. A hermetically sealed housing containing the refrigeration compressor transmission and oil supply reservoir is connected to the suction side of the compressor to equalize the pressure in the housing and the suction to the compressor is constructed with a restriction such as an orifice or a venturi to create a pressure drop or is of a size small enough to create a pressure drop when refrigerant flows through the line. The pressure drop is sensed by a pressure differential switch to anticipate sharp drops in pressure in the housing. The flow of refrigerant to the compressor is throttled in response to predetermined pressure drops to prevent a sharp drop in pressure within the transmission housing and thus prevent vigorous boiling of refrigerant from the oil reservoir.

Abstract: An apparatus is disclosed for use in venting the products of combustion from a power combustion system such as an induced draft furnace. The apparatus includes a housing having three openings and a baffle. One opening in the housing receives the gaseous products of combustion from the power combustion system. A second opening in the housing is connected to a flue pipe which directs the products of combustion from the housing to an outlet vent. The third opening in the housing has a spillage damper or movable panel which can cover the third opening. The panel is pivotally connected to the outside of the housing above the third opening. When the pressure within the housing is less than the surrounding atmospheric pressure the panel is forced closed by this pressure. The panel is forced open and the products of combustion in the housing are vented to the surrounding atmosphere when a pressure greater than the surrounding atmospheric pressure is present within the housing.

Abstract: The present invention relates to a self-checking safety switch control circuit for a power combustion system. The circuit comprises a safety switch, a combustion blower relay, a thermal pilot switch, and a fuel supply system. The safety switch operates to detect flow through the combustion system. The safety switch either operates the pilot switch directly or operates the fuel supply system directly to shut down the system if no flow through the combustion system is detected. The circuit has a self-checking feature because combustion cannot be initiated in a subsequent cycle of the system if the safety switch remains in the proven condition from the previous combustion cycle.

Abstract: A method of trimming a resistance element is disclosed which comprises cutting transversely into one side of the element until the measured total resistance of the element increases by a fraction 1/N of a fixed percentage of a desired total resistance value. The fraction 1/N is approximately equal to the path length of the resistance element divided by the designed width of the transverse cut and the fixed percentage is equal to the percent deviation of the initial total resistance of the element from a nominal, desired resistance value. After the transverse cut is made, a longitudinal-type cut is made at a distance, equal to the length of the transverse cut, from the edge of the element having the transverse cut to isolate a portion of the element from the remainder of the element so that the isolated portion has the desired total resistance. This method is particularly suitable for use with computer controlled laser trimming systems used to mass produce resistance elements.

Abstract: A method of arc welding is disclosed. Specifically, a method of pulsed DC arc welding is disclosed wherein the pulse width of the current pulses are modulated to maintain a constant time averaged power flow to the work pieces being welded. This method of arc welding is especially useful with a type of pulsed DC arc welding wherein the ratio of peak current to maintenance current is maintained at a selected high value and the current is cycled in a time duration whereby oxides on the surface of the work pieces are dissipated as the weld is made. When used with this type of pulsed DC arc welding the present method is especially suited for fluxless welding of aluminum work pieces, such as thin wall aluminum tubing used in making heat exchangers for air conditioning systems.

Abstract: This invention relates to a method and apparatus for shutting down a combustion system when a pressure greater than atmospheric pressure is present in the flue pipe of the system. The apparatus comprises a connector means for connecting the flue pipe of the system with the surrounding atmosphere and a thermal switch which is in thermal contact with and responds to the gases within the connector means. The apparatus is especially useful as a safety device for shutting down an induced draft combustion system when the flue pipe of the system is blocked. Also, the apparatus can be used with a combustion system having a flue outlet vent which is also used as the outlet vent for another combustion system.

Abstract: A control system for operating a vapor compression refrigeration system to prevent oil pump cavitation during startup of the refrigeration system is disclosed. The control system includes a differential pressure switch which is connected on one side to a reservoir which is in fluidic communication with the refrigeration system evaporator or compressor suction line. The pressure switch is connected on its other side directly to the evaporator or compressor suction line. In operation, the reservoir fills with vaporous refrigerant from the refrigeration system when the refrigeration system is shut down and the vaporous refrigerant flows through a restrictor valve back to the refrigeration system at startup of the refrigeration system. The size of the reservoir and restrictor valve are selected so that the differential pressure switch is activated and a control is generated when too rapid a decrease in evaporator or compressor suction line pressure is detected.

Abstract: A vent cap having a quick release fastener for connecting the vent cap to a flue pipe of a furnace or other such combustion system is disclosed. The fastener is designed for attachment to a tubular stub connector of the vent cap and has a clip portion for engaging a slot in the flue pipe to lock the vent cap and flue pipe tigether between the clip portion and a shoulder portion of the fastener. The vent cap is easily disconnected from the flue pipe by rotating the vent cap about the longitudinal axis of the flue pipe to remove the clip portion of the fastener from the slot in the flue pipe and then, pulling the vent cap apart from the flue pipe.