Types and operating points of the jack
A jack is a light lifting device that uses a rigid lifting member as a working device to open a heavy object through a small stroke of a top bracket or a bottom bracket. Jacks are mainly used in factories, mines, transportation and other departments for vehicle repair and other lifting and support work. The structure is light, sturdy, flexible and reliable, and can be carried and operated by one person.
At present, the most common jacks on the market mainly have the following categories:
1. Electric jack: The inside of the jack is equipped with a pressure-preserving device to prevent over-pressure. If over-pressure, the jack will not return to a certain position. The special structure can double protect the jack. After the jacking device is installed on the submersible device, It can achieve the goal of achieving high stroke at low altitude.
2. Screw jack: The thread of the screw jack has no self-locking effect and is equipped with a brake. When the brake is released, the weight can be quickly lowered by itself and the return time can be shortened, but the structure of the jack is complicated. The screw jack can support heavy objects for a long time, and the large lifting weight has reached 100 t, which is widely used. After the horizontal screw is mounted on the lower part, the weight can be traversed at a small distance.
3, hydraulic jack: used in the hydraulic transmission system as an intermediate medium, to transfer and convert energy, when used also in the hydraulic system, the lubrication, anti-corrosion, cooling, washing and other functions.
However, when operating this jack, some operational points still need to be mastered:
1. Jacking operation: The jacking height of the jack should not exceed the effective topping. When lifting a large object (such as a girders), the two ends should be separated and raised, and one end should be lifted and lowered, and the other end should be padded, padded, and stabilized. The jack is not allowed to be overloaded.
2. Foundation of the jack: The foundation of the jack should be stable, solid and reliable. When jacks are placed on the underside, roads or other suitable materials should be placed to enlarge the area of force.
3, the placement of the jack: When placing the jack on the soft ground, the wooden block should be placed under the jack to protect it from the force and tilt down. When the weight is raised, the weight should be placed under the support pad at any time, but the hand cannot be mistaken into the danger zone. During the placement process of the jack, the line of action of the center of gravity of the load is kept consistent with the axis of the jack. During the jacking process, the risk of pinching and tilting of the jack due to the deflection of the foundation of the jack or the horizontal displacement of the load should be strictly prevented. It is necessary to prevent the jack from slipping in contact with the metal surface of the heavy object or the smooth surface of the concrete, and if necessary, the hardwood block is used.
Precautions when using a three-jaw puller