"proved able to" is correct and usable in written English.
You can use it to describe an accomplishment or success. For example, "He proved able to complete the project in record time."
None of them proved able to help.
But only Washington proved able to "levitate" above the fray.
Clozaril proved able to help some people with schizophrenia when all other drugs failed.
It was the first time that mammals had proved able to regenerate hair cells.
Then the problem was Saddam Hussein, who proved able to survive defeat.
"In a crisis, Europe is isolated, and she has proved able to overcome that".
Banks' share prices have rebounded and they have proved able to raise capital from private hands.
In experiments, 35 years after leaving school, people have proved able to identify 90% of their classmates.
When the mortgage default wave struck, the banks proved able to rig the market to obscure its impact.
Though a poor draughtsman, Johnson proved able to design well and quickly and could afford to build what he liked.
In this case Henry proved able to distinguish the wakes of paddles whose widths varied by 2.8cm or more.
