Abstract: A magnetic differential pressure indicator is provided for detecting and indicating a pressure differential thereacross that is greater than a predetermined value in a fluid system, having a port that permits introduction or withdrawal of fluid for testing of operability under the predetermined pressure differential, and having a bimetallic element that prevents false actuation of the element at abnormal temperature, and a deactuator for the bimetallic element that permits such testing of the indicator via the port for operability even at such abnormal temperature.

Abstract: The combination of a vacuum cleaner and dust container wherein the latter is provided with an air pervious portion connected to an attachment plate in the form of cardboard and the like. The attachment plate is provided with an inlet for dust-laden air. The attachment plate has a pressure-sensitive element, the movement of which indicates the degree of clogging of the dust container without the use of seals or filters.

Abstract: An indicating device for vacuum cleaners, or similar apparatus, utilizing a dust container. The indicating device such as a diaphragm, is under the influence of a pressure differential and is movable against a force of a spring to give a visual indication from the outside of the vacuum cleaner of the degree of filling of the dust container therein. The motor of the vacuum cleaner has a motor regulator and the overall arrangement is provided with a unit for continuously varying the tension of the spring against the force of which the indicating device is movable.This invention relates to an indicating device for vacuum cleaners or similar apparatus having dust container with means which under the influence of a pressure differential is movable against the force of a spring and has a signalling device visible from the outside of the means for continuous visual indication of the degree of clogging of the dust container.

Abstract: A magnetic differential pressure indicator is provided for detecting and indicating a pressure differential thereacross that is greater than a predetermined value in a fluid system. A thermal lockout effective even at high internal fluid pressures prevents false actuation of the magnetic indicating means at low temperatures due to increased viscosity of the system fluid.

Abstract: A dirty filter indicator for use with an air filter for an internal combustion engine, the filter comprising a replacement for an ordinary wingnut used to hold the outer cover of the air cleaner in position. The replacement nut has a bypass passage through it which communicates with the interior of the filter so that if the filter becomes dirty and clogged, a lightweight ball which is located in this passage and is normally biased to one position moves to a second position to indicate that the filter is dirty.

Abstract: A pressure differential indicator for indicating a change in a fluid pressure differential across a component in a fluid system, such as an oil filter, has piston means, means for communicating fluid pressures of said system upstream and downstream of said component to opposite sides of said piston means, respectively, and differential means associated with the piston means for normally balancing the resultant forces of said pressure on opposite sides of said piston means at a given predetermined pressure differential across said component whereby said piston means is responsive to an increase or decrease in the pressure differential above or below said predetermined differential pressure to indicate a clean or clogged filter condition. Means are provided for holding the piston means in its last position upon relief of said first and second pressures to indicate the operating filter condition when the system is not operating.

Abstract: A differential fluid pressure indicating device for use in conjunction with a filter body carrying a filter element which provides an exteriorly visible signal when the differential pressure across the filter element exceeds a predetermined amount. The device comprises a housing having a cylindrical chamber in which a rotationally constrained piston is axially slidably disposed and movable between a first and second axial position while resilient means urge the piston towards its first axial position. The inlet fluid pressure communicates with one axial end of the piston while the outlet fluid pressure communicates with the other axial end of the piston. When the differential pressure across the filter element exceeds a predetermined value, the inlet fluid pressure moves the piston from its first to its second axial position and releases a spring loaded exteriorly visible member which rotates from a first to a second rotational position.