Using an IR remote control receiver like the TSOP as a beam-break detector is not exactly what it is designed to do. It works, but with the following limitation:
The TSOP has an Automatic Gain Control in its 40Khz receiver. When you shine a continuous 40 Khz IR beam on it, the AGC loop adjusts itself for the prevailing signal level. It is very sensitive to a momentary reduction in the 40Khz IR carrier; but if the interruption lasts too long (more than about 1 second), the AGC loop begins to readjust itself, and as it does, the output of the TSOP returns to the inactive (high) state. When the TSOP is being used to receive the IR pulse code, none of the interruptions in the IR carrier last more than a few ms, so the AGC loop time constant has a problem following long interruptions....
You will need to test how long the output of the TSOP stays low when you block the IR beam. If it goes back high (even thought the beam is still blocked) in less than a second, then your 1 second delay to pull-in the relay will require a triggerable one-shot like a 555. A one-shot triggered on the low-to-high transition would work to drive your relay, too.
If the output of the TSOP stays low for 2 or 3 sec while the beam is blocked for longer, then you would need a one-shot triggered on the high to low transition of the TSOP output which has a 1 sec period, and the relay would be pull-in while (TSOP low) AND (one-shot LOW).