Abstract: A frost deposition detector for an air cooler disposed in a refrigerating chamber. A first signal is generated when the electric current flowing through the motor of the air blower for the air cooler, the value of which is adjusted with respect to the voltage variation across the motor and the air temperature change in the refrigerating chamber, reaches a threshold value which is proportional to the initial current value corresponding to the state of no frost deposition. A second signal is generated when the difference between the air temperature in the chamber and the air cooler temperature reaches a threshold difference, which can be set at a desired level. The detector generates a defrostor activation signal when and only when both first and second command signals are generated.

Abstract: A sewage treatment apparatus having a rotary shaft and a plurality of rotary plates secured to the rotary shaft in an axially spaced-apart relationship, each of the rotary plates being adapted to be rotated while it is partly dipped in sewage within a treating tank,a plurality of holding members provided fixedly around the rotary shaft for rotation therewith, andthe rotary plates being secured such that at least one rotary plate is fixedly held at its central end portion between every two adjacent holding members.

Abstract: An improvement in the suction mechanism of a rotary engine is provided in that two peripheral ports each with a rotary valve are formed in the peripheral wall of the rotor housing having a trochoidal inner peripheral surface and that during the first half period of the suction stroke one of said peripheral ports is opened by the action of a rotary valve provided therein to supply rich mixture into the combustion chamber and during the last half period of the suction stroke the other peripheral port is opened by the action of a rotary valve therein to supply air into said combustion chamber.

Abstract: An oil seal means of a rotary piston engine wherein an oil seal ring is mounted in an annular oil seal groove formed as a cut in a side wall portion of a rotor, wherein the oil seal ring has at least one projection radially projecting from its front circumferential edge portion, said projection being in engaging relationship with a corresponding notch formed at an annular opening edge portion of said annular oil seal groove for the purpose of preventing the ring from circumferentially sliding along the annular oil seal groove.

Abstract: A rotary piston engine of the type having a trochoidal inner surface of a center housing and an eccentrically rotating polygonal rotor, wherein an air or fuel injection opening provided in a side housing wall is confined within a region limited so as to be outside of an outer envelope of traces of a side seal and inside an outer envelope of traces of a corner seal, said opening having a contour smaller than that of said corner seal.

Abstract: An ignition system for rotary piston engines is disclosed wherein a plurality of ignition plugs are arranged and disposed in the combustion chamber in the directon of the rotation of a piston and connected to a common ignition coil so that one of them may be selectively energized depending upon the changing engine operations. The optimum ignition timing may be secured to minimize the pollutions in the exhaust gases.