The driver tried to leap away when the machine apparently became unbalanced and began to tip over, Police Chief Scott M. Hedenberg said.
But it knocked him down and a portion landed on the lower half of his body, the chief said.
Fellow workers and a police officer who was at the scene lifted the machine together, freeing the victim, Hedenberg said.
The North Arlington Volunteer Emergency Squad arrived quickly and the patient was taken, alert and conscious, to University Hospital in Newark, he said.
His condition couldn't immediately be determined.
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