Non-return valve for a hydraulic vehicle power brake system, and hydraulic vehicle power brake system

A hydraulic vehicle power brake system, comprising:

• a brake master cylinder operable by muscular energy;
• a power brake pressure generator;
• and
• a brake fluid reservoir, wherein the brake master cylinder is connected to the brake fluid reservoir by a non-return valve, which is configured to allow for a flow in a flow-through direction from the brake fluid reservoir to the brake master cylinder and which has a valve opening spring which keeps the non-return valve open until a specified counterpressure is reached in a closing direction counter to the flow-through direction, so that the non-return valve closes only once the specified counterpressure in the closing direction has been exceeded.

A hydraulic externally-powered vehicle brake system, comprising:

• a brake master cylinder operable by muscular energy;
• a power brake pressure generator;
• and
• a brake fluid reservoir;
• a test valve;
• and
• a first non-return valve that is hydraulically parallel to the test valve;
• wherein:
• the brake master cylinder is connected to the brake fluid reservoir by way of the test valve and the first non-return valve;
• the first non-return valve is configured to allow for a flow in a flow-through direction from the brake fluid reservoir to the brake master cylinder and block against a flow-through in an opposite closing direction;
• the test valve is switchable into a first switch position and into a second switch position;
• when the test valve is in the first switch position, flow can occur through the test valve from the brake fluid reservoir to the brake master cylinder and also from the brake master cylinder to the brake fluid reservoir;
• and
• when the test valve is in the second switch position, (I) flow from the brake fluid reservoir to the brake master cylinder is blocked and (I) flow from the brake master cylinder to the brake fluid reservoir (i) is blocked as long as a specified counterpressure is not reached and (ii) can occur when there is at least the specified counterpressure.