启用禁用的按键?

我试图阻止在表单上使用enter键进行双重提交,但在提交数据后,我似乎无法重新启用按键。以下是我的部分代码:

$(".adauga-clasa").submit(function() {
  var adaugaClasa = $('input[type=text]', this);

  adaugaClasa.keypress(function(event) { if (event.keyCode == '13') { return false; } });

  $.ajax({
    type: "POST",
    url: "/clase/do-add",
    data: dataString,
    dataType: "json",
    success: function(data) {
      // this doesn't work
      adaugaClasa.keypress(function(event) { if (event.keyCode == '13') { return true; } });           
    }
});