Method and apparatus for sorting contaminant material from processing material

A sorting apparatus for sorting contaminant materials such as rocks and metal from processing materials such as wood chips and the like, comprising:

• material receiving means having a surface portion for receiving a layer of material including both said contaminant and said processing materials;
• materials delivery means for impingingly depositing said layer of material on said surface position;
• sensing means engaging said surface portion for sensing vibration of said surface portion due to impingement of said layer of material thereon and for generating signals in response thereto;
• signal discriminating means for receiving said signals generated by said sensing means and distinguishing between signals produced by impingement of said contaminant material from those produced by impingement of said process material on said surface portion, and for passing only signals produced by impingement of said contaminant material, said signal discriminating means including means for distinguishing between the amplitudes and durations of vibration of said surface portion caused respectively by said processing material and said contaminant material;
• trap means downstream in the movement of said layer of material from said surface portion and movable between an inoperative position in which said layer of material flows in a normal flow path past said trap means to an operative position for diverting from said normal flow path a portion of said layer of material containing said contaminant material;
• and
• activating means for receiving said signal passed from said signal discriminating means and for activating said trap means to move from said inoperative position to said operative position in response thereto and for further causing said trap means to move from said operative position to said inoperative position after sufficient time to permit said contaminant material to be diverted.

A method of sorting contaminant material such as rocks and metal from processing materials such as wood chips mixed to form a continuous layer of material, comprising the steps of:

• impingingly striking a layer of material on a surface which can be vibrated thereby;
• sensing vibrations of said surface;
• generating signals corresponding to said vibrations;
• distinguishing between signals generated in response to impact of said processing materials from response to impact of said contaminant material by distinguishing between both the amplitudes and durations of vibration of said surface caused respectively by said processing material and said contaminant material;
• activating a material flow diverting means only in response to a signal generated by impact of said contaminant material on said surface, so as to divert the flow of a portion of said layer of material containing said contaminant material from the normal flow path of said layer of material;
• and
• deactivating said material flow diverting means after said portion of material has been diverted, so that said layer of material subsequent to said portion returns to the normal flow path.