// Set the joint to bounce off when hitting the lower limit
hingeJoint.limits.minBounce = 1;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
void Awake() {
hingeJoint.limits.minBounce = 1;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

def Awake():
hingeJoint.limits.minBounce = 1