US 6,418,829 B1 · Power tool safety device

A power tool safety device for a power tool having a table defining a working surface, a cutting tool disposed adjacent the working surface with at least a portion of the cutting tool extending above the working surface and a guard moveably disposed adjacent the working surface, the guard covering the at least a portion of the cutting tool extending above the working surface, the safety device comprising:

a proximity detector detecting a predetermined relative proximity between the guard and the working surface;
and
an interlock system coupled to the proximity detector and responding to the detecting of the predetermined relative proximity by the proximity detector, the interlock system preventing use of the power tool when the proximity detector does not detect the predetermined relative proximity between the guard and the working surface and enabling use of the power tool when the proximity detector does detect the predetermined relative proximity between the guard and the working surface.

A power tool safety device for a power tool having a table defining a working surface, a cutting tool disposed adjacent the working surface with at least a portion of the cutting tool extending above the working surface and a guard moveably disposed adjacent the working surface, the guard covering the at least a portion of the cutting tool extending above the working surface, the safety device comprising:

a proximity detector detecting a predetermined relative proximity between the guard and the working surface, the proximity detector including at least two permanent magnets permanently mounted on the guard in spaced apart relationship and at least two reed switches, each reed switch permanently disposed beneath the working surface of the table in opposed relationship to a different one of the permanent magnets, the reed switches having a sensitivity to a magnetic field that is selected to cause the reed switches to close when the guard is properly positioned in guarding relationship to the cutting tool;
and
an interlock system coupled to the proximity detector and responding to the detecting of the predetermined relative proximity by the proximity detector, the interlock system preventing use of the power tool when the proximity detector does not detect the predetermined relative proximity between the guard and the working surface and enabling use of the power tool when the proximity detector does detect the predetermined relative proximity between the guard and the working surface, the interlock system including a circuit that is responsive to the at least two reed switches and that disables use of the power tool unless each of the permanently disposed reed switches is closed.

A power tool safety device for a power tool having a table defining a working surface, a cutting blade disposed adjacent the working surface and a guard disposed to provide protection from the cutting blade, the safety device comprising:

a proximity detector detecting a predetermined relative proximity between the guard and the working surface;
and
an interlock system that is responsive to the proximity detector, the interlock system preventing use of the power tool when the proximity detector does not detect the predetermined relative proximity between the guard and the working surface, the interlock system including a circuit coupled to the proximity detector, the circuit enabling use of the power tool when the proximity detector does detect the predetermined relative proximity between the guard and the working surface and enabling continued use of the power tool after use has been initially enabled even if the proximity detector thereafter does not detect the predetermined relative proximity between the guard and the working surface, the interlock system including a bypass circuit having a bypass switch having a bypass state and a nonbypass state, the bypass circuit enabling use of the power tool when the bypass switch is in the bypass state whether or not the proximity detector detects the predetermined relative proximity between the guard and the working surface.

A power tool safety device for a power tool having a table defining a working surface, the table having an aperture extending therethrough in a direction generally perpendicular to the working surface and a cutting blade disposed adjacent the working surface, the safety device comprising:

a guard disposed to provide protection from the cutting blade to an operator;
an insert having a working surface disposed in the aperture such that the working surface of the insert is substantially coplanar with the working surface of the table;
a proximity detector located on the insert on a side thereof opposite the working surface of the insert, the proximity detector detecting a predetermined relative proximity between the guard and the proximity detector;
and
an interlock system coupled to respond to the detecting of the predetermined relative proximity by the proximity detector by enabling use of the power tool when the proximity detector detects the predetermined relative proximity between the guard and the proximity detector and preventing use of the power tool when the proximity detector does not detect the predetermined relative proximity between the guard and the proximity detector.

2 more elements

A power tool comprising:

a table defining a working surface, the table having an aperture extending therethrough;
a cutting tool disposed within the aperture and extending beyond the working surface;
an electric motor secured to the table on a side of the table opposite the working surface and coupled to drive the cutting tool;
a guard disposed above the working surface of the table and protecting an operator from the cutting tool, the guard having a standby position, being movable to accommodate a work piece as the work piece is being cut by the cutting tool and returning to the standby position after cutting of the work piece;
a proximity detector detecting a predetermined relative proximity between the guard and the working surface;
and
an interlock system coupled to the proximity detector, the interlock system responding to the detecting of the predetermined relative proximity by the proximity detector by enabling energization of the motor when the proximity detector detects the predetermined relative proximity between the guard and the working surface and by preventing energization of the motor when the proximity detector does not detect the predetermined relative proximity between the guard and the working surface, the interlock system including a bypass switch having a bypass position and a nonbypass position, the interlock system enabling energization of the motor whether or not the predetermined relative proximity is detected when the bypass switch is in the bypass position.

4 more elements

A power tool safety device for a power tool having a table defining a working surface with an aperture extending through the table and working surface, a cutting blade disposed to extend through the aperture to cut a work piece held against the working surface, an electric motor coupled to rotationally drive the cutting blade and a guide plate disposed on the working surface and having a leg extending through the aperture to a location beneath the table, the safety device comprising:

a guard disposed to protect an operator from the cutting blade, the guard being movably attached to the guide plate and moving to accommodate a work piece as the work piece is being cut by the cutting blade;
a proximity detector located near the working surface and detecting a relative proximity between the guard and the working surface, the proximity detector including at least one permanent magnet secured to the guard and at least one magnetic field strength detector disposed beneath the working surface and detecting a magnetic field emanating from the at least one magnet;
and
an interlock circuit responsive to and electrically coupled to the proximity detector, the interlock circuit being coupled to enable energization of the motor when the proximity detector detects the relative proximity between the guard and the working surface and to prevent energization of the motor when the proximity detector does not detect the relative proximity between the guard and the working surface, the interlock circuit being coupled to enable continued energization of the motor after energization has been initially enabled even if the proximity detector no longer detects the relative proximity between the guard and the working surface, the interlock circuit including a key operated bypass switch having a bypass position, the bypass switch being coupled to allow energization of the motor whether or not the proximity detector detects the predetermined proximity when operation of the power tool is initiated while the bypass switch is in the bypass position.

1 more element

A power table saw comprising:

a table defining a working surface, the table having an aperture extending therethrough in a direction generally perpendicular to the working surface;
an arbor disposed beneath the table;
a motor mounted on the arbor, the motor having an electric starting circuit to start the motor and a separate power circuit to power the motor;
a cutting blade coupled to be rotationally driven by the motor, the cutting blade being disposed to extend through the aperture;
a guard moveably disposed above the working surface and at least partially covering the cutting blade, the guard protecting an operator from the cutting blade;
an interlock system including a proximity detector detecting a predetermined relative proximity between the guard and the working surface, the proximity detector including at least one permanent magnet permanently attached to the guard and at least one normally open magnetic reed switch disposed on a side of the table opposite the working surface, each reed switch being located at a detection location opposite one of the at least one permanent magnet, each magnetic reed switch having an open state and a closed state and being coupled in series between the electric starting circuit and a power source, each reed switch detecting the predetermined relative proximity between the guard and the working surface by detecting a magnetic field intensity at the reed switch detection location by remaining in the open state when the predetermined relative proximity is not detected and by switching to the closed state when the predetermined relative proximity is detected, the interlock system responding to the state of the at least one reed switch by preventing use of the power table saw when any switch of the at least one magnetic reed switch is in the open state by disconnecting electrical power from the electric starting circuit and enabling use of the power table saw when each of the at least one magnetic reed switch is in the closed state by coupling the power source with the electric starting circuit, the sensitivity of each reed switch to a magnetic field being selected to cause each reed switch to close when the guard is properly positioned in guarding relationship to the cutting blade, the power circuit of the motor being separate from the starter circuit of the motor and being connected to enable continued use of the power table saw after use has been initially enabled and the power table saw has been started even if one of the at least one magnetic reed switch switches to an open state after the power table saw has been started;
a slotted insert disposed within the aperture through the table with the saw blade extending through the slot, the insert having the at least one reed switch secured thereto at a location adjacent to the cutting blade;
and
a bypass circuit having a key activated bypass switch having a bypass state and a nonbypass state, the bypass circuit responding to the bypass state of the bypass switch by selectively bypassing the interlock system by coupling a power source directly to the starting circuit in response to the bypass state of the bypass switch.

6 more elements

Power tool safety device

Life of this patent

Power tool safety device

Life of this patent

Abstract

Claims34