Could you please 是can you please 更为礼貌、委婉的说法,并不是过去式,是“能否麻烦你……”、“请你……”的意思,更侧重“能否”及客观情况；回答时要注意,eg：A:“Could you please open the window?”肯定回答 B:“Of course”；否定回答：B:“Sorry,I can't open it because the windows are locked on the train.”
而Would you please 含有说话者一定的希望,期待对方愿意做某事的意味,“请你……”,更侧重“愿否”及主观能动；回答时要注意,eg：A:“Would you please open the window?”肯定回答：B:“OK”；否定回答：“I'm sorry,but don't you feel it is a little bit too cold outside?”
尽管两者有小小差异,但是在日常口语中,似乎两者经常通用,并没有区分得那么明显.
https://www.zybang.com/question/494332f29a80adc175e3898d4529317b.html