| 摘要 |
A system for locking the wheels of a dolly for a cleaning device has a brake arm that has one end that is hinged to the base of the dolly. The brake arm pivots between a disengaged position and an engaged position where a stop on an opposite end of the brak e arm engages the circumference of one of the wheels on the dolly. A spring biases the brake a rm to the disengaged position. The spring can be mounted on a pin that is seated on th e base and extends through a slot in the brake arm. An operator-engagable lever is used to move the brake arm from one position to another. The lever can be hinged to the pin, pivoting into a nd out of a locked position in which the lever presses the brake arm into the engaged position. A cam surface on the lever is shaped so that moving the lever to one side of a critical point causes the lever to be biased toward the locked position, and moving the lever to the other side of the critical point causes the lever to be biased toward the unlocked position. The part of the lever that abuts the brake arm when the lever is in the locked position can be a flat section on the cam surface.
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