Read a BLOB field and convert RTF

Question

I need to read a BLOB field where there is a text in RTF and convert to another format not being RTF in a select.

select utl_raw.cast_to_varchar2(dbms_lob.substr(obs)) 
from entidade

anyone knows any kind of cast ? I tried some but unsuccessfully.

is bringing in that way.

{\rtf1\ansi\ansicpg1252\deff0{\fonttbl{\f0\fnil\fcharset0 Arial;}} \viewkind4\uc1\pard\lang1046\fs16 Sempre 950.\par revisar todas as pe\'e7as \par \par }