Patent Application
20080303683
1. Field of the Invention
The present invention relates to an economical force sensitive switch. More particularly, the switch, includes a microswitch assembly which is operative to stop a machine or the like, until a structure of the machine producing the force on the switch, is repositioned.
2. Prior Art
It has previously been proposed, in U.S. Pat. No. 6,731,219, owned by applicant, to provide a complex, expensive force sensitive switch comprising a housing and a movable member movable relative to the housing upon having a predetermined force applied thereagainst by an adjacent moving structure when the structure becomes misaligned, with the movable member engaging a load cell assembly within the housing which will produce an alarm signal and will stop the adjacent structure from moving.
It has been since determined that a less expensive, less complex functional embodiment can be created by replacing the load cell assembly of the prior embodiment, with a microswitch assembly, allowing use thereof in areas where economy is a concern.
According to the invention there is provided an economical force sensing switch comprising a housing and a movable member movable relative to the housing upon having a predetermined force applied thereagainst by an adjacent moving structure when the structure becomes misaligned, the movable member being positionable relative to a microswitch, and acting thereon to engage the microswitch within the housing, to produce a visual indication and cause stoppage of motion of the adjacent structure. A secondary optional thermal switch may also be incorporated.
Perusing the Figures in greater detail, it will be understood that the force sensitive switch made in accordance with the teachings of the present invention and generally identified by the reference numeral 10, comprises a body 12 made up of a rigid housing 14 made from metal or other substantially rigid material and a movable member 13 which is movable toward and away from the rigid housing 14, with a suitable flexible diaphragm 16 engaged therebetween.
Within the housing 14 is mounted an economical microswitch assembly 17. Acting on the microswitch 17 is a set screw 18 secured to the movable member 13 and suitably guided thereby through an opening 19, in the diaphragm 16, to permit force to act on the microswitch 17 in one direction only. The moveable member 13 is restrained from movement in directions other than the direction of action on the microswitch, by the diaphragm 16. It will be understood that the diagram 16 is preferably made of a metal, such as steel so that it is rigid in all directions of force except in the direction of actuation. Attached to the diaphragm 16 is the movable member 13 which may comprise a suitable button, plate, disc, arm, or sphere which may be hardened to resist the action of wear. A cover washer 23 positioned between the diagram 16 and the micro switch assembly 17 incorporates a surface 28 which will not allow the moveable member 13 to move excessively as it will be restrained by contact with a rigid stop 30 in the form of a switch bracket 30.
The assembly of the movable member 13 is so dimensioned that when the diaphragm 16 has been deflected to the design limits, and well before the elastic limit is exceeded, the surface 28 of the washer 23 contacts the rigid stop 30 which may be the bracket 30 supporting the microswitch 17 itself, and prevents further force on the movable member 13 from over-stressing the microswitch 17. When the rigid housing 14 of the switch 10 is mounted solidly to one part of a machine (not shown), misaligned motion of another part of the machine (not shown), adjacent the movable member 13, will cause a force to be applied to the movable member 13.
Therefore the switch 10 can be used to detect relative displacement or misalignment between two parts of a machine. This detection is particularly applicable, but not limited, to machines such as belt conveyors or belt elevators (not shown) where it is necessary to detect that movement of a belt of the machine into an undesirable or misaligned position has occurred. In such application, the switch 10 would be mounted to a rigid part of a machine in such a position that if the moving belt of the machine was misaligned laterally, it would generate a force onto and against the movable member 13 of the switch 10. In such application, the force sensing switch 10 may be arranged to warn of, or control, such an “out of bounds” condition.
The signal can produce a visual indication through the preferred LED 46, and can pass through a cable 55, suitably attached to the machine in known manner, to cause motion of the adjacent structure, such as the belt, to cease, upon misalignment.
Various circuits capable of actuating the LED 46, for use in the switch 10, are illustrated in
In
One further point which may not be obvious from the description and drawings is that the diagram 16 is made out of steel or other metal so that it is rigid in all directions of force except in the direction of actuation of the switch 10.
It will also be understood by those skilled in the art that various structures of the circuitry described above may be mounted on a circuit board, if desired.
It will also be understood by those skilled in the art that the present embodiment is more economical than that previously proposed and therefore is available to a greater proportion of the purchasing public.
As described above, the force sensing switch 10 provides a number of advantages, some of which have been described above and others of which are inherent in the invention. Also, modifications may be proposed to the switch 10 without departing from the teachings herein. As an example, any simple, economical, equivalent structures, which could be used in place of the microswitch, should be considered within the scope of the teachings herein. Accordingly, the scope of the invention is only to be limited as necessitated by the accompanying claims.
