Abstract: A container body is sealed by means of a lid made of a flexible sheet having an insulative property and an antenna made of an electrically conductive material which is laminated upon the lid. According to this construction, when the container body is exposed to microwaves within a microwave oven, microwave energy is concentrated at a position near the front end of the antenna and the microwave energy is converted into heat energy, whereby the lid is opened by means of the thus converted heat. The lid can thus be precisely partially melted so as to form an opening of a predeterminedly suitable size.

Abstract: An apparatus for detecting pinholes in cans comprising a dark box consisting of a light seal plate and a window, a photodetector detecting electrically the outer penetration of light, and light sources disposed around the can. The light seal plate has a groove for receiving an open end of a can therein and is of a hardness greater than that of the can. The groove of the light seal plate communicates with a trap. The surface of the groove is black non-luster.

Abstract: An internal pressure inspecting method and system for determining the degree of unevenness of the surface of an elastic cover of each of one or more hermetically sealed containers, the unevenness being produced according to the internal pressure. The distance from a fixed position exterior of the hermetically sealed container to said cover surface is determined by measuring the change in inductance utilizing the action of electromagnetic induction, at a plurality of points i.e. the center and peripheral portions thereof. A value is derived by calculation of the difference between a mean value of both measured values at any one point in the peripheral portion and at the position on the diametric line which is in symmetrical relation therewith with the center of the container cover as the center of symmetry, and the measured value at the center of the container cover. The internal pressure of said hermetically sealed container is determined from this value.

Abstract: A method and apparatus for inspecting the internal pressure of hermetically sealed containers wherein a sound wave of free damped oscillation exicted at the elastic wall of a hermetically sealed container is converted and detected as an electrical signal, analysis is performed for natural self-correlation function of this detected signal by using logical operation circuits, and thus, the adequacy of the internal pressure is discriminated by measuring the period of such function.