Vaadin 7.6.X push Tomcat 7 Liferay 6.2

Hello,

I'm new in vaadin and liferay. I would like to use the push tchnology.
In liferay 6.2, I change the version of vaadin from 6 to 7.6.1

I have added the jar for the push
I have added the @push annotation

Then i have one button, when I clicked on, a background thread is sleeping then watch a notification.
But Now, I always need to click on a button or anything else to watch the notification.

I think, it's possible to refresh the UI with the push. But I don't know where is the problem

public void buttonClick(ClickEvent event) {
     if (event.getButton() == pushButton1) {
            new Push1Thread().start();
     }

class Push1Thread extends Thread
    {
        public void run() {
            try {
                Thread.sleep(5000);
                      
                final UI localUi = UI.getCurrent();
                localUi.access(new Runnable() {
                    public void run() {
                        // Here the UI is locked and can be update                 
                        Notification.show("Je suis réveillé push 1", Notification.Type.ERROR_MESSAGE);    
                    }
                });            
            } catch ( InterruptedException e ) {
                e.printStackTrace();
            }
        }
    }

Can anyone help me ?
Thanks a lot
Bertrand