Lifting machine is widely used for material handling. In recent years, some foreign experts pointed out that the material handling engineering technology is the weakest in modern industry, the most imperative area to focus on, but is also the most potential, the most promising area, put forward the material handling technology is the concept of the third profit source. Material handling machine usually includes lifting machine, transportation machine, loading and unloading machine, storage machine, industrial handling vehicles and hydraulic machine, a total of 6 categories of products. The material handling machine in our country is used to call crane transport machine. Because lifting machine has many varieties, functions, and other characteristics, it is at the dominant position of material handling machine, it is also the first application of weighing technology.
Lifting machine is one of handling equipment, which is used to carry on the rising, falling and moving of the materials in batch mode. In order to make the lifting machine lifting and weighing at the same time, thus people have the ideas and wishes to weighing on heavy machine.
Lifting machine application weighing technology has more than 200 years of history. In city of Munich Bavarian State Bureau of weights and measures, the preservation of around 1780 weighing suspension load of wall type spring balance; there is still one in Hamburg right now.
In 1760, the fixed jib crane, it is equipped with a decimal scale made in 1858. In the first half of nineteenth Century, the crane (crane) scale is famous for the name of "the Swedish ship scale". In 1932, within the error scale with the crane sling has been able to reach any load 0.2%, obtained type approval.
With the breakthrough of digital technology, especially the progress of electronic weighing technology, promote the development of mechanization, automation, integration and intelligent. Due to the continuous expansion of the scale of industrial production, increasing production efficiency, to promote large-scale, high-speed and specialized lifting machine with automation, intelligence and information technology performance characteristics. Modern weighing technology has led to the application of all kinds of heavy machine in the working environment directly involved in materials handling, transport, lifting, sorting, stacking, storage distribution and even, sometimes also can measurement, identification, tracking and management of materials directly and so on.
At present, the weighing device used in hoisting machine on the function is usually divided into electronic steelyard and special weighing device . Electronic balance is widely used, the more relevant, this does not explain. Special weighing device is mainly refers to the lifting machine has been widely used in the weight limiter.
a. Definition
Weight limiter is a detection of lifting weight to prevent the heavy machine in the overload operation and of weighing protection device, also known as crane overload limiter or crane load limiter.
b. Provisions of "safety rules for crane machine"
GB6067 - 85 "hoisting machine safety regulations stipulates: capacity bigger than 20t bridge crane, heavier than 10t gantry crane overload limiter shall be installed; other tonnage of overhead and gantry crane and electric hoist single beam and double beam crane should equipped with overload limiter.
c. The composition of the weight limiter
The weight limiter is composed of two parts, the resistance strain gauge type weighing sensor and the weighing control instrument. Weighing sensor for the detection of lifting weight; weighing control instrument according to lifting weights are identified, corresponding control signal is output.
d. Characteristics
Lifting weight limiter is the most important feature of the effective combination of the specific structure of the heavy machine, to ensure that the use of weighing sensors and weighing control instrument does not destroy the safety of the crane. At the same time, we should meet the functional requirements of reliable performance, convenient maintenance and high measuring accuracy.
According to the actual structure of the electric hoist single beam and double beam crane, play weight limiter usually adopts the plate ring type or stuck rope type weighing sensor, installation position at the fixed end of the steel wire rope; weighing control instrument usually installed in the cab or control button station above.
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