Water Surface Switch

Abstract

A float switch for opening and closing a circuit in response to the level of a liquid comprising a permanent magnet which is disposed loosely around a protection tube enclosing a lead switch, the magnet being slidable along the tube to open or close the switch contacts depending on the level of the liquid.

Description

The present invention relates to a water surface switch which aims at obtaining a floating control switch inexpensive yet reliable by utilizing a lead switch instead of an expensive mercury switch hitherto used.

The invention will be fully understood from the following descriptions with reference to the annexed drawings in which:

FIG. 1 is a partial sectional view of a portion of a water surface switch according to the invention, showing its position at a lowered water level during drainage by a pump;

FIG. 2 is a partial sectional view of a portion of the water surface switch showing its position at a raised water level.

Referring in more detail to the drawings, the invention comprises a float 1 in which is mounted a ring-shaped permanent magnet 2 disposed loosely around a switch protection tube 9. The magnet is retained around the tube by a stop member 5 mounted on the bottom of the tube.

Mounted in tube 9 is a switch 7 which includes contacts 3 and 4. The contacts are normally separated as shown in FIG. 1. A rubber or resin coated electric cord 6 extends away from the switch for electrical connection to the pump motor. The cord 6 is attached to a weight 8 which controls or limits the bending of the cord. The weight 8 is fixed vertically so that movement of the switch as the water level rises or lowers is relative to the weight.

In the operation of the device, when the water surface is lowered as illustrated in FIG. 1, the contacts 3 and 4 are kept open as the permanent magnet 2 is moved down the tube to the position thereof in FIG. 1 where it contacts the stopper 5. Consequently, no electric current will flow through the motor and the draining pump will be inoperative.

When the water level, and thus the float, rise to the position illustrated in FIG. 2, the permanent magnet 2 will slide down along the outer surface of the lead switch protection tube 9 until it comes to and stops over the contacts 3 and 4. As a result, the contacts 3 and 4 are closed by the magnetic force of the magnet 2, thereby putting the switch circuit in a closed position, and energizing the pump motor to initiate the draining operation.

As the pump keeps on draining water, the float moves from its FIG. 2 position to its FIG. 1 position. As the float moves downwardly past an intermediate, horizontal position, the magnet 2 will slide downwardly over the tube 9 until it contacts the stopper 5. Consequently, the contacts 3 and 4 will be opened and the pump motor stopped.

In order to make the permanent magnet 2 properly slide from its position of FIG. 1 to that of FIG. 2, and vice-versa, the coefficient of friction between the permanent magnet 2 and the lead switch protection tube 9 preferably has a certain predetermined value. At such value, the permanent magnet 2 slides into the position of FIG. 2 from that of FIG. 1 only after it has reached a certain upward inclination, and thus the pump will be made to start its operation when a certain water level is reached. Similarly, the permanent magnet 2, once having come to its position of FIG. 2, will move into its position of FIG. 1 only when the lead switch protection tube 9 has reached a certain level of downward inclination in accordance with the decrease in the water level. Up to that point, the pump will continue to be operated.

It will be apparent from the above description that the present invention is characterized by its relatively low cost of manufacture, the unfailing opening and closing actions of the switch because of the utilization of a permanent magnet, and the certain operation of the pump until the water level is lowered to such an extent as to stop the pump motor.

Claims

What I claim is:

1. A float switch for opening and closing the circuit in response to the level of a liquid comprising a housing, a switch protection tube mounted in said housing in spaced relation thereto, a lead switch mounted in said protection tube, said switch having a pair of contacts, a ring-shaped permanent magnet disposed loosely around said protection tube for sliding movement therealong, means on said protection tube for confining the axial movement of said magnet along said tube, said magnet in one position of said float resulting from a rise in the liquid level being radially aligned with said contacts for closing the same and thus said circuit, and in a second position of said float resulting from a drop in the liquid level being displaced along said tube at a position relatively remote from said contacts thereby permitting opening of the same and thus said circuit.

2. The switch of claim 1 wherein the coefficient of friction between said permanent magnet and said protection tube is such that said permanent magnet slides along said tube only when said switch reaches a predetermined angle of inclination relative to the liquid level line.