purchaser should not see the RFx response before the deadline

Hi everyone:

     I have a question. In my system when i create a RFx in srm portal and the bidder responses it. the RFx response should not be seen by purchaser before the deadline. But in my system the purchaser can see it .

     The type of my RFx is Bid. Could you tell me how to configure the srm system to achieve this goal?

Best Regards

Charles