Are springs allowed?

Does anyone know if we are allowed to use springs?

Yes. We are allowed to use springs.

Yes, but make sure its done in a safe and controlled manner. (Safety cables through the springs and a safe post match/pit compression release plan)

Springs are legal under [R36], and as many others have stated, make sure they’re safe.

[R36]
The only legal source of electrical energy for the Robot during the competition is one MK ES17-12 12VDC non-spillable lead acid battery, or one EnerSys NP 18-12 battery, as provided in the 2012 KOP. This is the only battery allowed on the Robot.

Batteries integral to and part of a COTS computing device are also permitted (i.e. laptop batteries), provided they’re only used to power the COTS computing device.

Non-electrical sources of energy used by FRC Robots, (i.e., stored at the start of a Match), shall come only from the following sources:
A. Compressed air stored in the pneumatic system, stored at a maximum pressure of 120 PSI.
B. A change in the altitude of the Robot center of gravity.
C. Storage achieved by deformation of Robot parts.

You can even have them pre-compressed. Emphasis mine.