Blake's father, who's also named Jacob, says he and Blake's mother's were nervous at first to talk with the Democrats' Presidential ticket ... but says Biden and Harris calmed them down. The elder Jacob said, "I don't think people understand the worry of a mother. That's her baby."

He revealed how the conversation went down Friday morning on CNN's "New Day" ... saying it felt "like I was speaking to my uncle and one of my sisters -- literally, literally." Jacob's father added, "It felt like they knew what was going on. And, they didn't act like they were in a hurry to go anywhere. They spent time with us."

When asked if President Trump has reached out, Jacob said, "That's a negative." Trump also never mentioned Jacob Blake's name during his RNC nomination acceptance speech.

Jacob's father, who referred to Biden and Harris as President and Vice President, also touched on his son's leg being shackled to his hospital bed.

As we reported ... Blake's dad was furious after finding out his son was handcuffed to his hospital bed during a Wednesday visit. He questioned why that was even necessary since Jacob's paralyzed from the waist down after taking 7 shots to the back from a cop. Jacob's father said his son asked, "Why did they shoot me so many times?"

Jacob's dad pointed out ... "He can't go anywhere. Why do you have him cuffed to the bed?"