It is actually used to connect a wheelchair and a bicycle. The part consists of a spring where it can be compressed.

Can anyone tell me the name of this connector part?
Thanks.

 

No idea what you're talking about. A picture might help...

 

yes, a picture would help.

 

I googled "connect wheelchair to bicycle" and I'm thinking you may be asking about a lynch pin.
https://www.google.com/search?q=lynch+pins&tbm=isch

-tg