Productivity enhancement for band saw

1. A powered machine of a type configured to be operated by one or both hands of a human operator when presenting material for cutting or shaping, within a working space that forms a hazardous zone defined by a height, a width, and a depth and in a position in relation to a frame of the machine, the machine comprising:

a saw blade formed as a flexible band bearing saw teeth and passing in frictional contact around a drive wheel that is driven when in use by a motor comprised of a saw drive, the saw blade passing though the working space and passing around an idler wheel; and

a safety protection apparatus that generates an output signal upon detection of a hazardous event within the hazardous zone when the powered machine is in use;

an actuator device, including

a decoupling actuator disposed in a manner so as to act directly upon the saw blade to disengage the saw blade from the saw drive, and

a braking actuator that applies a brake to the saw blade,

the decoupling actuator and the braking actuator configured to operate in combination to halt a motion of the saw blade,

wherein the decoupling actuator includes a first actuator that resiliently maintains a first axle supporting the idler wheel in a first position farther from a second axle of the drive wheel such that, when in use, the saw blade is maintained under a working tension and the saw blade is coupled to both the drive wheel and the idler wheel via static friction until receiving the output signal from the safety protection apparatus, upon which the first actuator, through an over-center mechanism, removes support from the first axle so that the first axle moves to a second position closer to the second axle thereby removing the working tension from the saw blade and decoupling the saw blade from both the drive wheel and the idler wheel.

2. The powered machine as claimed in claim 1 , wherein the first axle of the idler wheel is maintained in position by an over-center latch held in place against a force imposed by tension within the saw blade by the first actuator.

3. The powered machine as claimed in claim 1 , wherein the first axle of the idler wheel is configured to be reset under a manually initiated self-resetting procedure that restores tension to the saw blade.

4. The powered machine as claimed in claim 1 ,

wherein the saw blade is operatively disposed to pass through the braking actuator, which includes a brake assembly with at least one brake shoe, and

wherein a second actuator is operatively connected to the brake assembly and is configured to hold the brake assembly in a disengaged mode when the second actuator is energised against compression spring pressure thereby allowing the saw blade to pass, and

upon receiving the output signal from the safety protection apparatus, the second actuator is de-energised and thereby permits the compression spring to force the brake assembly to close around and grip the saw blade so as to apply friction against the saw blade by contact with the brake shoe.

5. The powered machine as claimed in claim 3 , wherein the actuator device brings the saw blade to a halt within 40 milliseconds after receiving the output signal.

6. The powered machine as claimed in claim 4 , further comprising:

self-monitoring means for ensuring a safe maximum braking time is not exceeded, the self-monitoring means configured to bring the saw blade up to an operating speed while monitoring a saw movement speed, and then causes the output signal to be generated to cause the blade to stop, and further verifies that the saw blade has stopped within a predetermined time limit.

7. The powered machine as claimed in claim 1 ,

wherein, when the powered machine is in use, a pivotally mounted tooth holds a first block slidably moveable along vertical bars and resiliently supports, via a compression spring, a movable second block that bears a movable axle supporting the idler wheel,

wherein, when in the first position, the tooth is supported in place by the over-center mechanism including an over-center latch including a contact roller pivotally supported on a beam held in an over-center position around a pivot until the beam is pushed past the over-center position by a first solenoid actuator energized in response to the output signal, whereupon the working tension in the saw blade gives rise to a release force applied at the tooth and causes the idler wheel to fall and thereby remove tension from the saw blade and decouple the saw blade from the idler wheel.

8. The powered machine as claimed in claim 7 , wherein the first axle supporting the idler wheel is configured to be reset under a manually initiated self-resetting procedure that restores tension to the saw blade and restores the over-center latch to the over-center position.

9. The powered machine as claimed in claim 4 , wherein the second actuator is capable of being set into a disengaged mode by a pneumatic cylinder that applies a compressive force to the compression spring to the saw blade whereupon the solenoid is maintained in an energized state until the output signal is received.

10. The powered machine as claimed in claim 4 , wherein the decoupling actuator in sequential combination with the braking actuator apparatus brings the saw blade to a halt within 40 milliseconds after receiving the output signal.

11. The powered machine as claimed in claim 4 , wherein a self-monitoring procedure, for ensuring that a safe maximum braking time is not exceeded, includes bringing the blade up to an operating speed while monitoring a saw blade movement speed, then generating the output signal to cause the blade to stop, and verifying that the saw blade has stopped within a predetermined time limit.

12. The powered machine as claimed in claim 4 , wherein the second actuator is a solenoid.