please be gentle with me because sometimes i don't explain things well enough!

but i will try.

I have a oven with 2 zones going from right to left:

<<<<<< ZONE A <<<<<<<<<<<<<< ZONE B <<<<<<<<<< 

I have to control a gate at the end of conveyor (this is controlled by others), the product comes into the oven and enters through ZONE B through to ZONE A and this will start a dwell time of 10mins (example) then release the product.

But if i have a product in ZONE A and another product enters into ZONE B then i need to allow the time to be adjusted so that for example if the product in ZONE A is released and the product in ZONE B has already been in the oven for 5 mins then moves into ZONE A, i then have to release the product when the total dwell time is complete.

I have not used shift registers in this way before and i wondering for some pointers in the correct way of doing this, if indeed this is the best way of doing it.

Thanks

If i have not explained very well then please ask for further information.

current inputs and outputs:

I1 = Zone A Sensor

I2 = Zone B Sensor

Q1 = Gate Solenoid

edited: added inputs/outputs

Hi, could you share your program?

What is the LOGO are you using? What is the logo softcomfort as well?

Not sure uploading the program will help, this part of the program is not completed.

it is not 100% clear why you would want to use a shift register. Is it not possible to control the gate to release a product when the gap between products is enough? 

Consider making a hand sketch of your problem and indicate the positions of the x2 sensors and x1 gate. I assume the conveyor is under the control of the other contractor. I assume the speed of the conveyors are kept constant.

Is the average gap between products more than the time that the minimum 5min gap? What prevents a build up of product at the gate? Is it possible for the gate to separate two products from one another?

Sorry i should have been more specific, the track has powered carriages on it that are controlled by others and the gap between them is controlled by a laser measuring device that works out the spacing/speed between each carriage.

what i proposed to do it operate a flag with pneumatic solenoid so this is placed in front of the sensor to stop the carriage,

This bit is fine but the trouble i have that there are 2 zones from right to left 

<<<<<<< Zone A <<<<<<<<< Zone B <<<<<<<<<<<<<<

The carriages enter from the right and move into Zone A and stop and the then start a dwell time of say 20 minutes but say after a carriage has been in Zone A for 15 minutes and another carriage enters into Zone B and after the dwell time of 20mins has elapsed the carriage in Zone A is released and the carriage in Zone B moves forward into Zone A this now needs a dwell time of 15  minutes because its already been in the oven for 5 minutes.

I hope i have explained it a little better, like i say the carriage control is done by others and works well with the laser system in place. i am just unsure how to go about transferring the time etc.

You have a storage for two cars. That does not need a shift register. Use two timers. Have memory bits select which timer is used. For example M1 and M2.

If the car passes the sensor from Zone B -> A then M1 is set when M1 is off. Else have M2 set. M1 lets B001 timer run; M2 lets B002 run. If B001 runs out, open the gate and reset M1. If B002 run out, open the gate and reset M2.

The front car will always have its timer run out first. So have a timer running for each car that enters Zone A. A timer running out means the gate can release the front car.