Loading a 3D object from Assetbundle mutliple times in different scenes

I have an AssetBundle for a 3d object. In Vuforia, when one Image target is detected I want it to load the scene that will show me the downloaded 3d object. This works for me if I run the script once.But when I go back to the camera view and again detect the image target,I am not able to get the object. How do I make it in such a way that the object is loaded and displayed everytime the image target is detected without re-starting the app.

This is my code: AssetBundle bundle;

 void Start()
 {
 StartCoroutine("Download");
 }
 IEnumerator Download()
 {
 url="http://myurl";
 WWW myasset= WWW.LoadFromCacheorDownload(url,1);
 yield return asset;
 
 bundle = myasset.assetBundle
 if(Assetname=="Box")
 {
 bundle.LoadAsync(Assetname,typeof((GameObject));
 Instantiate(bundle.Load(AssetName));
 }
 }