Abstract: A method and apparatus are disclosed for measuring changes in relative distance between a float and both a signal source and a detector. Also disclosed is the advantageous use of such an apparatus for detecting losses as little as 0.02 gallons of liquid per hour from a tank otherwise capable of storing 1,000 gallons or more of such a liquid.

Abstract: A method for detecting small leaks in a tank storing a liquid by measuring changes in the location of a float suspended in the liquid. The method includes the steps of sealing the float to prevent the condensation of vapors within the float, positioning the float at a preselected depth, modulating an emitted signal by an amount which varies with the changes in the location of the float, and detecting the modulated signal. Changes in the signal are indicative of small changes in the location of the float and small leaks in the tank.

Abstract: A method for detecting small leaks in a tank storing a liquid by measuring changes in the location of a float suspended in the liquid. The method includes the steps of sealing the float to prevent the condensation of vapors within the float, modulating an emitted signal by an amount which varies with the changes in the location of the float, and detecting the modulated signal. Changes in the signal are indicative of small changes in the location of the float and small leaks in the tank.

Abstract: An apparatus for detecting small changes in the location of a float, has, in combination, a signal generator for emitting a signal having a characteristic, a detector for detecting a modulated signal by producing a response signal directly related to the characteristic, a support for positioning the signal generator and the detector, and a float weighted to float at a desired depth in a selected liquid. Also included are a reservoir for holding a measuring medium, a plug for preventing condensation of vapors within the float, with the float movably connectable to the support, and the detector and the signal generator fixedly connectable to the support so that the signal when emitted by the signal generator will have the characteristic of the signal modulated by the measuring medium by an amount which varies with changes in location of the float to produce a modulated signal.

Abstract: An improved self-service gasoline pump is designed to insure payment for the fuel which has been delivered by the pump. The pump includes a switch mechanism which must be operated by the ignition key of an automobile prior to operation of the pump. Upon insertion of the ignition key into the switch mechanism, the mechanism automatically clamps and retains the key until the key is released by operation of a remote switch at the cash collection station. The switch mechanism includes a key actuated switch in the key slot. Upon actuation of the switch, a fuel pump circuit is closed and a solenoid locking circuit is also closed which causes the key to be clamped. A remote unlocking switch may be operated to release the solenoid locking circuit.

Abstract: An improved apparatus for removing lubricating compositions from crankcase oil pans of internal combustion engines through the oil dipstick well of the engine involves signalling means, acting in response to the amount of vapor flowing to the vacuum chamber of the apparatus to signal, preferably audibly signal, the completion of removal of lubricating composition from the crankcase oil pan.An improved method for removing lubricating composition from crankcase oil pans is also disclosed.