Transact SQL :: Repeatedly Assign Set Of Dates To Each ID?

I have a table with 3 columns , let say (PatientID  int, AppointmentDate date, PatientName varchar(30))

My source data looks in below way..

PatientID        AppointmentDate      PatientName
  1                 01/01/2012          Tom
  2                 01/10/2012          Sam
  3                 02/15/2012          John

I need output in below way..

PatientID        AppointmentDate      PatientName
  1                 01/01/2012          Tom    (actual patient record)
  null              01/10/2012          Tom
  null              02/15/2012          Tom
  null              01/01/2012          Sam
  2                 01/10/2012          Sam     (actual patient record)
  null              02/15/2012          Sam
    null              01/01/2012          John
  null              01/10/2012          John
  3                 02/15/2012          John     (actual patient record)

I need t-sql to get above output. Basically the appointment dates are repeatedly assigned to each patient but only difference is patientid will be not null for actual patient record.
 
Create table sample (PatientID  int null, AppointmentDate date null, PatientName varchar(30) null)

Insert sample  values (1,'01/01/2012' ,'Tom'),
(2,'01/10/2012','Sam'),
(3,'02/15/2012','John')