Is there such a thing as a momentary relay?

I have a 24v latching solenoid. If you apply 24V to it, it immediately fires the bolt, and will stay that way even when the power is removed. If you apply reverse polarity 24V it will withdraw the bolt and stay that way with the power removed.

The problem I have is that I want to have it 'lock' and 'unlock' off another circuit, but it uses a keyswitch that is either always on or always off.

So basically when the switch is turned on, I just want to pulse a relay that has the solenoid attached to it, but relays seem to only be available that stay closed whilstever they are getting power. Is there a relay that will just click on momentarily (less than 2 seconds say, or as fast as 200ms) when power is applied?

Not directly. Does your switch have both Normally-Open and Normally-closed contacts (Form C, three terminals)? If not, could you replace the existing switch with one that does?

One of the simplest ways to have a relay to actuate for a short time when driven by a continuous voltage is to connect a capacitor in series with it. The capacitor will need to be able to discharge when the power is removed, so either it can have a large value (or else the current through it will turn on the relay) resistor connected in parallel with it or a resistor connected in parallel with the relay + capacitor.

Am I correct in assuming that you will have two relays; one to drive the solenoid one way, and another to return the solenoid to its starting position?

I think I will have to have two relays, yes.
Dougy83, do you mean a circuit like this? https://www.oldradio.com/current/cont2mom.htm
Would I have to change the values to run it off 24v?
Thanks
Andrew

I have a 2 pole toggle switch NC-COM-NO.
The circuit is for a lock on an electronic door. The existing magnetic latch isn't strong enough, so I want to replace it with a solenoid.
The toggle switch is connected to a controller that operates a motor to open the door.
Basically when the toggle switch is switched to NC it activates the 'stop' circuit and power is cut to the door motor. The switch is left in this position until the door is to be opened again.
So I want the switch to 'lock' the door when it is switched to NC.
I need the door to automatically unlock the moment the motor starts up, it has a 240v brake output that kicks in about a second before the motor starts up. I can put a transformer on the 240v brake output to get it down to 12v. I thought I could use the 12v to trigger the relay, but I need it to trigger momentarily.

I'm now confused. I initially though that had just two things; a toggle switch and a solenoid, where when the switch is flipped one way, the solenoid is pulsed positive, and when the toggle is flipped the other way, the solenoid is pulsed negative.

That can be done with no relays if the toggle switch can handle the solenoid current. However, it sounds like you have other requirements which you didnt disclose initially.

Dokworm, yes that circuit should do the trick. The capacitor value depends on the relay coil and the time you want it to stay on.

Yes, will need two such circuits; one for engaging the solenoid and one for disengaging the solenoid.