| 摘要 |
<p>A PNEUMATIC VEHICLE JACK: A pneumatic vehicle jack comprises a jack cylinder with a body and a piston rod assembly movable to each other, two levers pivoted to said body or piston rod assembly, located on either side of the longitudinal axis of the jack cylinder and carrying vehicle and ground engaging shoes, and two struts pivotally mounted between said levers on the one hand and said piston rod assembly or cylinder body on the other hand. A cartridge of compressed gas can be removably adapted onto said jack cylinder for actuating the same. Actuation of the jack cylinder causes the pivot points of the levers and struts to be brought closer together, to move the shoes away from each other. At the beginning stage of the actuation movement, the lever system comprising the levers and struts reduces the force exerted by the jack, and at the end of the said movement it increases said force. Because the volume occupied by the gas contained in the cartridge increases during the actuation of the jack, the force exerted by the jack cylinder progressively decreases. Thus, the lever system compensates for this decreasing force and a substantially constant force is exerted by the vehicle jack in its whole, and the raising movement of the vehicle is also progressive and constant.</p> |
