A hand brake is a mechanism installed on the vehicle braking device by means of man power as the motive power, and it is mainly used in railway wagons.  When the railway wagon is commissioning or is parking, by manually operate the hand brake with man power as the motive power, to produce the braking force, and the braking force is transmitted to the brake shoe through basic braking device, then the brake shoe is close to the wheel to produce braking.  The common hand brake usually comprises of a hand wheel, a chain, an enclosure, a drive shaft assembly disposed in the enclosure, bull gear and base, hand wheel and drive shaft assembly are connected, one end of the chain is fixed on the bull gear, and the other end is connected with the fixed pulley arranged at the bottom of the braked vehicle through a hand brake pull rod.  When braking, a hand wheel drives a pinion to rotate clockwise by a drive shaft, and then drives the bull gear to rotate counterclockwise, and the ratchet and pawl rotate oppositely.  When the bull gear rotates, the chain is wrapped around the bull gear spindle, thereby applying a braking force to the pull rod of the basic braking device.  When the hand brake is working, the opinion is connected with the drive shaft through a clutch, at this time, rotate the hand wheel, and the drive shaft will rotate; when an operator releases the hand wheel, the ratchet has a tendency of reverse rotation due to the gravity of the chain, however, with blocking effect of the pawl, the ratchet will not rotate, nor drive the chain to move, so as to maintain the braking effect.  When it is necessary to relieve, operate the clutch, to separate the pinion from the drive shaft.  At this time, the chain moves under the gravity, and drive the pinion to rotate relative to the drive shaft by the bull gear, to achieve remission operation.  However, this kind of hand brake has the following drawbacks: (1) when a convertible is coupled with a truck, usually there is interference of the hand brake hand wheel and the windshield; (2) The chain-hand brake pull rod and the wheel groove of the fixed pulley are not in a straight line, the design is unreasonable, which will not only affect the appearance, but also the transmission efficiency is low, easily leading to the wear of the fixed pulley and hand brake lever. 
In order to solve the interferences of hand wheel of hand brake and the bus windshield, the prior hand brake needs to offset 125 mm or more to the outside of the vehicle horizontally, which will lead to form a lateral shift of about 100 mm between the chain center at the chain winding shaft end and the chain center at the fixed pulley end.  Therefore, when 100 mm offset easily causes braking by the hand brake, the chain and enclosure are clamped, and the chain and movable pulley interfere, affecting the performance of the hand brake.  Besides, the excessive offset may cause decreased transmission efficiency of fixed pulley, and the poor visual effect worsens.  Through the structural analysis of the convertibles and hand brake, it is unable to guarantee the performance of the hand braking system of the truck only by adjusting the installation position of the hand brake on the vehicle to resolve the interference of the hand wheel of hand brake and the passenger windshield, and it is necessary to improve the structure of the NSW type hand brake.