a that gets fed to the crushing wheels 50 and 51 when a relatively light box 12 a is struck by the flat teeth 32 of the wheels the box may tend to bounce and u201c float u201d above the rotating teeth and the object will not be engaged and crushed however blades 16 which extend outwardly of the flat teeth 12 and are somewhat flexible will engage and push box 12 a downwardly to be fed to the passage between the wheels and the box 12 a will be crushed as shown in fig3 5 wheel 51 is biased to a closed position by the force of spring 77 connecting through arms 87 and 85 as depicted in fig6 when the teeth 52 of the rotating wheels 50 and 51 engage a non crushable object very high forces will be generated to push the wheels apart the spring 77 force tending to hold wheel 51 in a closed position will be overcome and wheel 51 will move swing pivot outwardly the passageway between wheels 50 and 51 indicated by the arrow line 81 will widen and the non crushable object 12 b will drop through the passageway into the non fluorescent waste container 44 swinging or pivoting wheel 51 thus provides the important function of protecting the wheels 50 and 51 as well as the overall machine 10 against damage refer now to fig6 for an additional detailed explanation of the operation of swinging pivoting wheel 51 the motor drive shaft rotates wheel 50 in turn a chain 55 connects sprocket 60 on wheel 50 to.