Progamming help

Hi all I am still very new to PLC programming and would like some help. I have to program a bottle rejector using siemens S7 and I have been getting a bit stuck with the logic. I was hoping someone here could help me with the program. The task is as follows: A fallen bottle is detected by a sensor and after a shot period of time a signal is sent to the cylinder to extend and push the bottle off the line. It seems like an easy enough problem but I cant figure out how to do it correctly. At the moment I can sense the fallen bottle but by the time the bottle gets to the reject cylinder the sensor is no longer positve and I no longer have a signel to initiate the cylinder. Also how do I deal with two fallen bottles one after the other? Any help with this would be appritated as I have already spent a couple of hours trying to get this right and have had no luck. Thanks.

You could use a "Shift register" (Word shift in siemens)and put a 1 into a word every time the sensor sees a fallen bottle.
Shift the data every time the machine completes a cycle (Or everytime a bottle passes).

At the reject station "Read" the particular bit - depending how many bottles there are between the sensor and the cylinder - then fire the rejector cylinder if the bit value is "1".

You could possibly use two timers - a delay off "SF" to remember the bottle is fallen, in series with delay on timer "SD" to tell the cylinder to extend now.

sound like a perfect case for a shift register.

This should help explain a shift register.

http://www.plcs.net/chapters/shift20.htm