Device
A telescopic (double-rod) jack is a mobile device designed to lift cargo and a vehicle during its maintenance and repair. The principle of operation of a double-rod jack is based on Pascal's law. The design of this device consists of two vessels connected to each other. They are filled with hydraulic oil, which, when pumped through a special valve, flows from one reservoir to another, creating excess pressure to lift the stem.
Double rod jacks consist of the following elements:
- cylindrical tank for storing working fluid;
- a piston that is driven by oil pressure;
- distributor, it is responsible for even distribution of pressure in the right direction;
- a filter that removes small particles and other contaminants from the oil;
- relief and discharge valves, designed to maintain a certain amount of pressure and return the stem to its initial position;
- pump responsible for pumping hydraulic oil and maintaining pressure.
Design features
On sale you can find two types of jacks, which will differ in the principle of lifting the working rod:
Varieties of a bottle jack
- Screw bottle jack. Consists of a coarse thread body and a ratchet nut. The advantages of this design are simplicity and the ability to work in any position. Maximum effort is limited by the applied muscular strength.
- Hydraulic bottle jack. It works on the principle of connecting vessels and develops an effort of several tons. The physical costs of lifting remain constant. There are two-rod (telescopic) and single-rod jacks.
In a hydraulic jack, the working fluid is a special oil, which is poured into the housing through a hole intended for this.
The principle of lifting the working rod is based on the use of Pascal's law for communicating vessels. The pressure in them is the same, and the gain in force is achieved by the difference between the areas of the working piston and the plunger, which works in a small vessel and serves to pump oil. Thus, a force of 2, 3, 5 tons and more is achieved.
The plunger pump drive can be manual using a special lever or a pumping oil station connected via a special adapter. The stem is lowered when oil is released into the upper part of the hydraulic cylinder, for which the bypass valve is opened (used for high-capacity jacks).
Hydraulic jack device
Peculiarities
Recently, jacks with low (side) pick up have been in great demand, since they make it possible to lift a load from a low working height. The design of such models is quite stable and reliable. In addition, they feature large-scale functionality. Lifting devices of this type are used not only for car repairs, but also during construction and other work related to the lifting of large-sized metal or other structures and loads.
The design also includes so-called springs that quickly reset the bayonets. In addition, the uneven surface of the jack prevents large objects being lifted from sliding, thereby ensuring safe operation. And a special lever allows you to use the greatest effort for lifting.
Views
Today on sale you can find telescopic jacks of various types - from stationary to portable and mobile. In addition, the lifting device may differ in size, principle of operation and design features. The most common types of double-rod jacks include the following.
Mechanical
Great for car enthusiasts. Its mechanism is driven by the physical efforts of a person. Such a jack is usually diamond-shaped and comes with a sliding mechanism, the main component of which is the lead screw. To lift a load using a mechanical device, it is necessary to turn the handle, while the lifting capacity directly depends on the screw thread (the wider the pitch, the higher the load can be lifted).
Among the mechanical double-rod jacks, rack and pinion models, in which a folding pick-up is fixed on a tripod, deserve special attention. Compared to other mechanical jacks, rack and pinion jacks are available with lifting heights from 500 mm to 1 m.
The main advantages of mechanical devices include: compactness (they take up little space in the garage), ease of use, good stability, reliability in operation and an affordable price. As for the shortcomings, such jacks cannot be overloaded with an unacceptable weight, and they also have low efficiency.
Hydraulic
This type runs on hydraulic oil. Its principle of operation is as follows: the drive pump creates oil pressure, which causes the plunger (piston) to move and starts the process of lifting the load to the desired height. After the working fluid enters the pump reservoir, the load begins to descend smoothly. The double-plunger jack has a lot of advantages, among which it is possible to single out a large carrying capacity, smooth running, high efficiency and mobility of the structure.
In addition, hydraulic jacks are expensive.
In turn, hydraulic jacks are subdivided into bottle jacks, rolling jacks and special jacks (hooking, diamond-shaped).
The most popular and functional are two-rod bottle models, they are characterized by a convenient design and a long service life.
The rolling jack has found wide application among motorists, it can be found in any garage. The design of the rolling device is in the form of a trolley with a rigid frame, which is able to withstand heavy loads. In addition, the structure includes a protection valve, it is triggered in the event of overloads and increases the safety of the device.
The main advantages of rolling jacks include:
- full autonomy;
- high efficiency;
- no need to spend time and effort;
- safe and convenient operation (can be used in any place where a breakdown has occurred).
There are no drawbacks to such units.
Classification of hydraulic jacks
Hydraulic jacks are classified into two types:
- Bottled. They have the simplest design, also called vertical - because of the corresponding axis of movement of the cylinder and piston. The use of this type of jack is permissible only when the load is at a certain elevation above the ground, otherwise it will not be possible to substitute the device under it. Due to its wide range of carrying capacities - from 2 to 200 tons - it is widely used in the automotive industry. Compact, has a large support area. Distinguish between single-rod and double-rod models;
Bottle jack for 10 tons
- movable. The principle of operation is similar to that of a bottle jack, however, in a rolling jack, the axis of the working cylinder is placed not vertically, but horizontally, and the piston is not directly aligned with the pickup - it is activated by the movement of the lifting lever.Continuing the comparison, this type of jack is more convenient to use when working with loads that are at a small distance from the ground - fixed on a special trolley, the jack is delivered directly under the load, after which it remains only to operate the lever. Such a device is less compact, more whimsical to the conditions of the area, however, it works much faster than an example.
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