Force sensor

Abstract

A force measuring apparatus includes a housing located with respect to an axis and having axially front and rear sections. A plunger is centered on the axis, supported by the housing for axial movement, and has axially front and rear spring supports. A load cell is fixed to the housing behind the rear spring support. A front spring structure is compressed between the front section of the housing and the front spring support of the plunger, urging the plunger rearward. A rear spring structure is compressed between the load cell and the rear spring support. The rear spring structure urges the plunger forward and applies against the load cell a force that is measurable by the load cell.

1 . A force measuring apparatus comprising: 
 a housing located with respect to an axis and having axially front and rear sections;    a plunger centered on the axis, supported by the housing for axial movement, and having axially front and rear spring supports;    a load cell fixed to the housing behind the rear spring support;    a front spring structure compressed between the front section of the housing and the front spring support of the plunger, urging the plunger rearward; and    a rear spring structure compressed between the load cell and the rear spring support, urging the plunger forward and applying against the load cell a force that is measurable by the load cell.    
   
   
       2 . The apparatus of  claim 1  wherein the spring structures together bias the plunger into a neutral position from which an external rearward force applied to the plunger will move the plunger rearward and increase the measurable force and an external forward force applied to the plunger will move the plunger forward and decrease the measurable force.  
   
   
       3 . The apparatus of  claim 1  wherein the plunger has a radially outwardly extending flange with front and rear surfaces that respectively comprise the front and rear spring supports.  
   
   
       4 . The apparatus of  claim 1  wherein the front spring structure includes a coil spring surrounding the plunger.  
   
   
       5 . The apparatus of  claim 1  further comprising an extension limiting structure that limits forward movement of the plunger to prevent full compression of the front spring structure.  
   
   
       6 . The apparatus of  claim 1  further comprising a retraction limiting structure that limits rearward movement of the plunger to prevent full compression of the rear spring structure.  
   
   
       7 . The apparatus of  claim 1  wherein the housing encases the spring supports of the plunger.  
   
   
       8 . The apparatus of  claim 1  wherein a front section of the plunger is located in front of the housing.  
   
   
       9 . The apparatus of  claim 1  wherein the front section of the housing defines an axially extending channel that closely receives the plunger so as to enable axial movement of the plunger while preventing radial movement of the plunger.  
   
   
       10 . The apparatus of  claim 1  further comprising prongs attached to the plunger and projecting radially outward from the plunger.  
   
   
       11 . The apparatus of  claim 10  further comprising a device with pockets that rotatably capture the prongs to couple the plunger to the device.  
   
   
       12 . The apparatus of  claim 10  further comprising a plate by which the prongs are attached to the plunger, that closely receives the plunger and from which the prongs project radially outward.  
   
   
       13 . The apparatus of  claim 1  further comprising a vacuum cleaner handle including a handle stem and a handgrip slidably attached to the stem, one of the stem and the handgrip being fixed to the housing, and the other of the stem and the handgrip being fixed to the plunger, for the force measurable by the load cell to be indicative of a force manually applied to the handgrip relative to the stem.  
   
   
       14 . A force measuring apparatus comprising: 
 a housing located with respect to an axis and having axially front and rear sections;    a plunger centered on the axis, supported by the housing for axial movement, and having a spring support;    a load cell fixed to the housing behind the rear spring support;    a spring structure compressed between the load cell and the spring support of the plunger, urging the plunger forward and applying against the load cell a force that is measurable by the load cell; and    a retraction limiting structure that limits rearward movement of the plunger to prevent full compression of the rear spring structure.    
   
   
       15 . The apparatus of  claim 14  wherein the housing encases the spring support of the plunger.