:URL Problem

I have a Problem with :url i have the following code:

:url => { :controller => :singlereceipts, :action => :update, :id =>
sr.id }

and the generated URL looks like this:
/singlereceipts/709689955

if i change :controller to "singlereceipts/update", the URL changes to:
/singlereceipts/update/index/709689955

and if i add :action => :update to the long controller, the URL changes
to:
/singlereceipts/update/update/709689955

I dont have a clue whats going on, i hope you can help me.

Greetings

Sven