Shredder for comminuting bulk material

A shredder comprising:

• a shredder box including an upper hopper for receiving material desired to be shredded and a lower discharge opening for discharging shredded material from the shredder box, the shredder box also including a screen mounting location located above the lower discharge opening;
• a shredder rotor positioned within an interior of the shredder box adjacent to a lower end of the upper hopper, the shredder rotor being rotatable about a rotor axis, the shredder rotor including a main rotor body and plurality of rotor teeth mounted to the main rotor body, wherein the rotor teeth define a cylindrical reference boundary at a time when the shredder rotor is rotated about the rotor axis;
• a shredder comb positioned adjacent to a lower end of the upper hopper, the shredder comb including comb teeth, the shredder comb being positionable in a shredding position in which the comb teeth intermesh with the rotor teeth and are located inside the cylindrical reference boundary, the shredder comb also being positionable in a relief position in which the comb teeth are outside the cylindrical reference boundary;
• a screen that is mountable at the screen mounting location for screening shredded material that moves past the shredder comb, the shredder being operable with the screen mounted at the screen mounting location and with the screen removed from the screen mounting location;
• and
• the shredder comb being operable in a first operating mode and a second operating mode, wherein when the shredder comb is in the first operating mode the shredder comb is moveable from the shredding position to the relief position upon a first force applied to the shredder comb by material being shredded to allow an obstruction to pass between the shredder comb and the shredder rotor, and wherein when the shredder comb is in the second operating mode the shredder comb is moveable from the shredding position to the relief position upon a second force applied to the shredder comb by material being shredded to allow an obstruction to pass between the shredder comb and the shredder rotor, the second force being lower than the first force;
• and
• a control system including a controller and a sensor in communication with the controller, wherein the sensor is operable to detect whether or not a screen is installed at the screen mounting location, and the controller is programmed to:
• a) operate the shredder with the shredder comb in the first operating mode at a time when the sensor indicates that the screen has been installed at the screen mounting location;
• and b) operate the shredder with the shredder comb in the second operating mode at a time when the sensor indicates that a screen has not been installed at the screen mounting location.