Adjustment and Control Features for a Power Tool

Abstract

Improvements to a table saw include a system for automatically adjusting the height of the cutting blade in relation to the height of the workpiece, a system for providing fine adjustment of the height or bevel angle of the saw blade or work surface, and a system for automatic speed control and shut-off for the saw blade.

What is claimed is: 
     
         1 . An adjustment system for a power tool having a table with a work surface for supporting a workpiece, a saw blade extending through a slot in the table surface, a carriage supporting the saw blade and a motor for driving the saw blade, the carriage supported relative to the table to permit relative pivoting and vertical translation between the saw blade and the table, the adjustment mechanism comprising:
 a motor;   a bevel adjustment component operably coupled to one or both of the carriage and the table to adjust the angle of the saw blade relative to the table surface;   a height adjustment component operably coupled to one or both of the carriage and the table to adjust the height of the saw blade relative to the table surface; and   a coupling between said motor and each of said bevel adjustment component and said height adjustment component, said coupling configured to selectively engage said motor to only one of said bevel adjustment component and said height adjustment component.   
     
     
         2 . The adjustment system of  claim 1 , wherein said coupling is configured to transmit power to one of said bevel adjustment component and said height adjustment component when the motor torque to said coupling is below a first predetermined torque value, and to transmit power to the other of said bevel adjustment component and said height adjustment component when the motor torque to said coupling is above a second predetermined torque value. 
     
     
         3 . The adjustment system of  claim 2 , wherein said coupling includes a slip clutch engaged to said one of said bevel adjustment component and said height adjustment component. 
     
     
         4 . The adjustment system of  claim 3 , wherein said coupling includes a centrifugal coupling engaged to said other of said bevel adjustment component and said height adjustment component. 
     
     
         5 . The adjustment system of  claim 1 , wherein:
 said motor includes a drive gear; and   said coupling includes;
 a shaft with a driven gear in meshed engagement with said drive gear; 
 a torque limiting coupling operably coupled to one end of said shaft; and 
 a centrifugal coupling operably coupled to the opposite end of said shaft. 
   
     
     
         6 . The adjustment system of  claim 1 , in which the carriage is pivotably supported on the table, wherein said bevel adjustment component includes:
 a worm gear selectively driven by said motor; and   teeth defined on an arcuate surface of the carriage and configured to mesh with said worm gear so that rotation of said worm gear pivots the carriage.   
     
     
         7 . The adjustment system of  claim 1 , wherein:
 said bevel adjustment component includes a first drive shaft operably coupled to one or both of the carriage and the table;   said height adjustment component includes a second drive shaft operably coupled to one or both of the carriage and the table; and   said coupling includes a slide clutch configured to operably couple said first drive shaft to said motor in a first position and to operably couple said second drive shaft to said motor in a different second position.   
     
     
         8 . An adjustment system for a power tool having a table with a work surface for supporting a workpiece, a saw blade extending through a slot in the table surface, a carriage supporting the saw blade and a motor for driving the saw blade, the carriage supported relative to the table to permit relative pivoting and vertical translation between the saw blade and the table, the adjustment mechanism comprising:
 a motor;   a bevel adjustment component operably coupled to one or both of the carriage and the table to adjust the angle of the saw blade relative to the table surface;   a height adjustment component operably coupled to one or both of the carriage and the table to adjust the height of the saw blade relative to the table surface;   a first coupling between said motor and one of said bevel adjustment component and said height adjustment component; and   a second coupling, separate from said first coupling, between said motor and the other of said bevel adjustment component and said height adjustment component,   wherein each coupling is configured to selectively engage said motor to only a corresponding one of said bevel adjustment component and said height adjustment component.   
     
     
         9 . The adjustment system of  claim 8 , wherein said first coupling is configured to transmit power to one of said bevel adjustment component and said height adjustment component when the motor torque to said coupling is below a first predetermined torque value, and to transmit power to the other of said bevel adjustment component and said height adjustment component when the motor torque to said coupling is above a second predetermined torque value. 
     
     
         10 . The adjustment system of  claim 9 , wherein said first coupling includes a slip clutch engaged to said one of said bevel adjustment component and said height adjustment component. 
     
     
         11 . The adjustment system of  claim 10 , wherein said second coupling includes a centrifugal coupling engaged to said other of said bevel adjustment component and said height adjustment component. 
     
     
         12 . The adjustment system of  claim 8 , wherein:
 said motor includes a drive gear; and   said first coupling includes;
 a shaft with a driven gear in meshed engagement with said drive gear; 
 a torque limiting coupling operably coupled to one end of said shaft; and 
 a centrifugal coupling operably coupled to the opposite end of said shaft. 
   
     
     
         13 . The adjustment system of  claim 8 , in which the carriage is pivotably supported on the table, wherein said bevel adjustment component includes:
 a worm gear selectively driven by said motor; and   teeth defined on an arcuate surface of the carriage and configured to mesh with said worm gear so that rotation of said worm gear pivots the carriage.   
     
     
         14 . The adjustment system of  claim 8 , wherein:
 said bevel adjustment component includes a first drive shaft operably coupled to one or both of the carriage and the table;   said height adjustment component includes a second drive shaft operably coupled to one or both of the carriage and the table; and   said first coupling or said second coupling includes a slide clutch configured to operably couple said first drive shaft to said motor in a first position and to operably couple said second drive shaft to said motor in a different second position.   
     
     
         15 . A safety feature for a power tool having a table with a work surface for supporting a workpiece, a saw blade extending through a slot in the table surface, a carriage supporting the saw blade relative to the work surface, and a drive motor for driving the saw blade, the safety feature comprising:
 a sensor operable to sense the passage of a workpiece beyond a location on the work surface in which the saw blade has made a cut through the entire workpiece and to generate a signal in response thereto; and   a controller for deactivating the saw blade in response to receipt of said signal.   
     
     
         16 . The safety feature of  claim 15 , wherein said sensor senses a change of an electrical parameter of the drive motor indicative of a change from load to no-load operation of said drive motor. 
     
     
         17 . The safety feature of  claim 15 , wherein said sensor includes a component configured to sense physical contact with the workpiece and positioned relative to the saw blade at a position in which the saw blade has made a cut through the entire workpiece. 
     
     
         18 . The safety feature of  claim 15 , wherein the component includes a spring-biased pressure switch that is depressed by a workpiece and that generates said signal when the pressure switch is released.