Based on the crossbow, there are developed several bows whith multiple arrows (or balls (bolos)) that quickly can be fired consecutively. Automatic or rapid fire bows.
The arrows sometimes have 2, but usually no stabilization feathers, so that they can be laid no matter how in the arrow magazine. It can not be as accurate with shooting, but they're not intended for accuracy, but for speed.
I suspect that they were primarily designed as a weapon of war and defense, to hit many attackers in quick succession.
But it can also be useful to animals (rabbit, pheasant, partridge...) that forage in groups, to catch more than one. With a normal (cross) bow have after the first shot, after the time for reloading all (other) animals chosen their heels.

The arrows are usually stacked in a small cartridge, where they only fit just on top of each other.
There are types that have a supply chamber at the bottom, like a machine gun. With the tightening of the string each time one arrow is pushed up by a spring.
Most models have a reservoir from above.
With the Chinese bow, the reservoir is part of the lever which is used to set tension on the string. At every span turn, an arrow also is placed and streaked away.
More frequent is a fixed tank. If the string is pulled back behind the arrow, he is fired immediately.
For tensioning of the string an ordinary claw can be used. The tension is limited to your arm strength. With a lever it can be increased, as in the Chinese bow. There are also types where the tension is made by such downward nod as flask at an air rifle.

With this rehearse bows several arrows can be shot per second.

On the Internet there are several ingenious models , search e.g. at homemade repeating crossbow. Trigger and loading mechanisms are often well shown and explained, sometimes even with instructions there.

https://www.youtube.com/watch?v=Yrv3nmOcv5M&feature=related