Sensor responsive to liquid level

Claim 1

Apparatus including a sensor assembly (10) and associated electrical circuitry the sensor being responsive to level of a liquid, the apparatus including in combination, a. float means (17) having a buoyancy such that it floats in the liquid, b. means (e.g., S-2) responsive to proximity to the float means adapted to energize an electrical circuit, c. pump means (47) to lower the level of the liquid, the pump being activated by the energized electric circuit, d. latching relay means (30), in the electrical circuit, adapted to be latched when the circuit is energized, constructed and arranged so that rise of the liquid from a low level to a particular higher level (23.1; 67) having effected proximity energizing the circuit as aforesaid, the latching means causes the circuit to remain energized, e. and means to unlatch the latching means so as to de-energize the electrical circuit, and wherein; the sensor assembly has at least one float, a. i. the float being a magnetic float having a magnet, b. i. the means (b) responsive to proximity to the float including at least one magnetic switch responsive to proximity to the magnet of the magnetic float; the sensor assembly being further characterized by f. an inner tube (12) having a lower end, g. a low level magnetic switch (S-1) secured within the inner tube near its lower end, h. the magnetic float having a central opening so as to be slidable of the tube, and means to limit downward motion of the float to a lowest position with respect to the tube, constructed and arranged so that in the lowest position the NC switch is opened by proximity to the magnet of the magnetic float, closing when the liquid, and with it the float, rises to a level at which the low level switch ceases to respond to the magnet, i. a NO magnetic switch ( S-2) secured within the tube spaced above the low level magnetic switch, the NO switch being adapted to close responsive to the magnet of the float when the liquid, and with it the float, rises to the particular higher level, j. and latching relay means (30) having latching means (37) controlled by the low level switch, and power contacts (39) controlled by the NO magnetic switch the power contacts when closed activating the means (c) aforesaid, the latching relay means being constructed and arranged so that the power contacts, having been closed as aforesaid, remain closed until the low level NC magnetic switch is opened by fall of the liquid such that the float resumes the lowest position opening of the NC low level switch unlatching the relay and opening the power contacts; the means to effect latching including, k. a low level NO magnetic switch (S-10) adapted to be closed by proximity of the magnet of the magnetic float when the liquid is at a low level, l. a signal means (54) in series with the NO magnetic switch across power buses (51, 52), m. an electromagnet (55) shunted across the signal means, n. a further NO magnetic switch (S-15) adapted to close when the electromagnet is energized, the low level and the further magnetic switches being in parallel, constructed and arranged so that when the NO low level switch closes as aforesaid, the signal means energized together with the electromagnet energizing of the electromagnet closing the further magnetic switch so that, notwithstanding the low level switch subsequently opens, the signal means remains energized, o. means (S-21) to open the further magnetic switch (S-15) thus effecting latching.