Springs

Happy Hacking keyboards use two types of springs:

• Conical springs, under each rubber dome, and
• A helical spring between the spacebar and slider

Conical Springs

From Deskthority:

[The Topre] switch consists of a slider in a housing over a rubber dome over a conical coiled spring over a printed circuit board. When the conical spring is compressed, a capacitive sensing mechanism on the PCB senses the keypress mid-actuation.

The spring itself provides very little resistance:

[The] conical spring provides only around 5 cN of actuation force and is therefore critical only for sensing keypresses.

Helical (Spacebar) Springs

In addition to the 60 (ANSI) / 69 (JIS) conical springs, each Happy Hacking Keyboard has a larger helical spring installed between the spacebar and its switch housing.

^{Source: eBay}

Thumb strength and the nature of most touch-typists resting their thumb/s on the spacebar while typing can lead to accidental spacebar actuation at the stock actuation weight of 45g, so the spring provides additional resistance on the spacebar to prevent this.