Abstract:
The 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 incorporating a set screw for engaging a microswitch within the housing at a predetermined position thereof to generate an alarm signal and will stop the adjacent structure from moving. A secondary optional thermal switch may also be incorporated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    1. Field of the Invention 
         [0002]    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. 
         [0003]    2. Prior Art 
         [0004]    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. 
         [0005]    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. 
       SUMMARY OF THE INVENTION  
       [0006]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0007]      FIG. 1  is a cross sectional view through the switch of the present invention. 
           [0008]      FIG. 2  is an exploded view of the switch of the present invention 
           [0009]      FIG. 3  shows various circuits by which the visual indicator, in the form of an LED, can be actuated. 
           [0010]      FIG. 4  is an exploded view of the switch of the present invention showing an optional secondary thermal switch incorporated therein. 
           [0011]      FIG. 5  is a top plan view of the switch of  FIG. 4 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    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. 
         [0013]    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 . 
         [0014]    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 . 
         [0015]    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. 
         [0016]    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. 
         [0017]    Various circuits capable of actuating the LED  46 , for use in the switch  10 , are illustrated in  FIG. 3 . 
         [0018]    In  FIGS. 4 and 5 , a further embodiment of the switch  10  is illustrated wherein a secondary optional thermal switch  60  is incorporated therein. The thermal switch  60  can be fitted within the housing  14  to detect any temperature rise which may be caused by a slightly misaligned elevator or conveyor belt which rubs contiguously against the movable member  13  with sufficient force to cause frictional heating but without sufficient force to actuate the microswitch. In this way, the switch  10  can provide detection of varied conditions of force and misalignment. In this embodiment, the thermal switch  60  is preferably seated on and fixed to the washer  26 . 
         [0019]    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 . 
         [0020]    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. 
         [0021]    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. 
         [0022]    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.