event.preventDefault doesn't work

I have this code below but can't get event.preventDefault() to work. The problem is, I already have other forms and it works fine. I'm sure you can help me. Here is the code:

$(document).on('dblclick','td.selecionaCodigoCliente', function(){
            //event.preventDefault();
            $("#mostraClienteSelecionado").html("Cliente [" + this.parentNode.children[0].innerText + "]: " + this.parentNode.children[1].innerText);
            $('input[name="salvaCodigoCliente"]').attr('value',this.parentNode.children[0].innerText);
        });

PS: The above code is for dblclick in the table.

$("#botaoSalvaOS").on('submit',function(event){
        $.post("salvaOS.php", $(this).serialize(),function(){
            $("#sucessoOS").html("Dados inseridos com sucesso");
        });
        event.preventDefault();
    })

PS: This glasses are for processing commits

After submitting the form, I got a PHP response. Here is the PHP code.

<?php
    include_once('db.php');

    $dataAberturaOS = date('d-m-Y');

    $codigoCliente = $_POST['salvaCodigoCliente'];
    $equipamento = $_POST['equipamento'];
    $marca = $_POST['marca'];
    $modelo = $_POST['modelo'];
    $nserie = $_POST['nserie'];
    $acessorio = $_POST['acessorio'];
    $observacao = $_POST['observacao'];
    $defeitos = $_POST['defeitos'];

    if(mysql_query("INSERT INTO ordemdeservico VALUES('NULL', '$equipamento', '$marca', '$modelo', '$nserie', '$observacao', '$acessorio', '$defeitos', '$codigoCliente', '$dataAberturaOS', '$dataAberturaOS', 'ABERTA')"))
        echo "Successfully Inserted";
    else
        echo "Insertion Failed";
?>

Thanks in advance.