Abstract
Plan
- Introduction
- 1. General information on portable percussion tools
- 2. Classification of chipping hammers
- 2.1 Standard sizes of chipping hammers
- 2.2 Classification of percussion instruments on the drive
- 2.3 Design features and a different operating principle hydraulic demolition hammers
- 3. The concept and principle of operation of the hydraulic Jackhammer
- 4. Mathematical simulation of working process of hydraulic impactor Jackhammer
- Conclusion
- List of resources
Introduction
Today, the portable impact mechanism, but simply put, Hammer is an indispensable assistant any Builder, contractor, or even an ordinary person, who started a small repair.
There are many varieties of chipping hammers, in my work I will consider hydraulic portable impact mechanism, because experience shows that their operation recently in our country and abroad is becoming more widespread, due to the fact that they have more impact energy at high frequency, compared with pneumatic and electric, that is why this topic is very relevant in our time, and particularly in our region.
The world's first hammer was invented in 1897 by engineer Georg Liner and since then this tool actively used all over the world.
Jackhammer percussion equipment is used for the destruction of different kinds of material.
This work is dedicated to the research of starting system and the choice of optimal parameters of hydraulic hammer system.
The main task is to analyse the different models of concept gidromolotka in order to select the most efficient workflow for further studies of bump stop (simulation) by mathematical modeling and optimization methods to determine the optimal design and operating parameters.
1. General information on portable percussion tools.
Jackhammer-mechanical hand tools percussion designed to loosen the soil, promerzšego and hard punching openings and holes in the brick walls of buildings, dismantling of the brickwork, cracking ice, coal production of various fortresses, mining ore, soft clay, shale and other construction and mining.
The executive body is usually a metal chisel or peak. Mechanization of the tool is the executive body of the series of mechanical pulses from the firing pin, which is driven by a drive. Frequency of exposure was 16.25 Hz. When the message bit of impact impulse is from reassembly cutting edge chisels affects the processing of material, cutting it or chopping.
Jackhammer is usually percussion machine with piston valve distribution. The inclusion of the hammer by pressing a hand to his arm. When you work a hammer firing pin makes a back-and-forth motion and at the end of the strikes on the shank of the spikes, Buchs-barrel hammer last spring. A worker operates a Jackhammer when otbojke rocks as a lever. Hammer turns off automatically when withdrawing forces with arms.The effectiveness of a Jackhammer depends largely on the bit-peaks to jackhammers. The peak directly affects the destroyable object.
As an intermediary between the hammer and the drummer, the peak for the Jackhammer should, on the one hand, effectively influence for destruction, and on the other hand, if possible, keep the hammer impact mechanism. That is too "rigid" peak will be unnecessarily fraying hammer, and "soft" will be less efficient in work. Many years of practice shows that approximately the lifespan of a Jackhammer, takes approximately ten of spades.
For jackhammer there are many different tips for your body to be selected depending on the type of planned activities, such as:
Drawing 1 – Peak-chisel
Peak-chisel is used to cut through any material for the destruction of brick walls, asphalt, frozen soil, granite. Variants peaks length 1500 mm.
Drawing 2 – Peaks crowbar
Tie-in the form of peaks crowbar choose if you want to loosen the soil or destroy asphalt or concreted surface.
Deicing, for cutting, crushing and asphalt edging, stripping walls of plaster layer if you need to clear a large area of concrete need peak-blade.
Drawing 3 – Peak-blade
Peak-rammer is used to perform work on the compaction of the soil, when you need to seal the seam, a crack in a place where it is not possible to make the usual way.
The correct choice of a jackhammer involves determining the purpose for which it is acquired. It is the scope and conditions of use determine the preferred characteristics of the instrument. Basic parameters–the number of beats per minute, power and energy of the impact. Also important is the level of vibration, noise at work. Also, pay attention to the body and the handle of a hammer, their ergonomics and functionality.
2. Classification of chipping hammers
2.1 Standard sizes of chipping hammers
Weight parameter of a jackhammer, not only is one of the main characteristics, but also acts as a basis for classification of the instrument to light, moderate and heavy models.
For light-weight class include thin model with a mass 6.5 kg. The main purpose of such strikers–use in everyday life. This tool has a relatively small capacity, so easy to use jackhammers to finish dismantling–the removal of ceramic tile, plaster, and so on. Thanks to its light weight, they are ideal for working at height or in a position with arms outstretched.
Middle class, the weight category from 5 to 10 kg, effective for different types of works mainly with horizontal position of the hands. They are used primarily for the repair or construction. With these hammers can dismantle monolithic concrete structures or remove old asphalt coating, for example.
Models heavy class, which starts from weight of 10 kg and in some cases can reach 32 kg intended for volume, complex and demanding high load operations. They are often used only on the street and in the "vertical-down." They are used in heavy industry and construction.
In order to minimize the weight of the product, modern manufacturing company hammers manufactured housing some hammers from a special kind of plastic that combines features such as light weight, durability and strength.
2.2 Classification of percussion instruments on the drive
On the type of drive jackhammers can be divided into four types–pneumatic, petrol, electric and hydraulic. Consider the main advantages and disadvantages of each.
First consider gasoline jackhammer. This striking mechanism starts from the internal combustion engine, integrated into the body of the hammer. The main advantage of such a tool is that it is independent of air, liquid or electricity, and does not require the application of a generator or compressor. However, it also has its drawbacks, such as high fuel (gasoline), toxic fumes, noise at work.
Drawing 4 – Gasoline jackhammer
Electric hammer works through the conversion of electrical energy into mechanical energy. Deep drilling and crushing dense materials electric jackhammer perfectly replaces percussion drills and hammers. This tool is used to hard work, the impact force him stronger than other instruments. However, this tool is contraindicated for use in areas of increased fire and explosion hazards. Furthermore, the product is sensitive to moisture, and regardless of the power source.
Drawing 5 – Electric jackhammer
Pneumatic hammer. Drive such a tool is powered by the pressure difference between the sides of the piston. The main advantages of this tool, ease of use, security, high performance and endurance, it makes this tool very popular not only in the structure of markets, but also in industry. The disadvantage of this arrangement is that its use requires optional equipment–compressor.
Drawing 6 – Pneumatic hammer
Hydraulic hammer has a greater advantage over other pneumatic equipment. Such a tool is much less expensive to maintain , because it does not require a compressor or motor. They have a greater impact energy at high frequency as compared with the pneumatic and electric . The main pluses also include long service life , lower maintenance costs and lack of harmful emissions . In my work, I will consider it a portable hydraulic shock mechanisms of action.
Drawing 7 – Hydraulic hammer
2.3 Design features and a different operating principle hydraulic demolition hammers
All mechanisms have developed Hydroshock as design features and different principle. By energy carrier distinguish devices using industrial oils, water-oil emulsions and process water.In most known Hydroplugger as the working fluid used industrial oils, and only in a few advanced options–wateroil emulsion.
Industrial water as the working fluid can significantly extend the scope of hammers, especially in those industries where it is important to use non-flammable liquids (coal industry, energy), or an important factor is the protection of the environment (eg, underwater works).
By type of drive performance of the hammer hammers are divided into three groups: hydraulic, hydro-pneumatic and hydro -mechanical.
The principle of operation are distinguished: direct action devices when working stroke of the striker is effected by fluid flow and return–by a spring or compressed air, reverse and double acting, when the energy flow forward and backward stroke of the striker. Analysis of the various structural schemes revealed that the most promising scheme is controlled by the camera to reverse, since acceleration is brisk carried fluid flow, pressure exceeds Impressed that provides intensive dispersal striker predudarnoy increase speed and energy of a single blow.
3. The concept and principle of operation of the hydraulic Jackhammer
The main elements of the tool are: the firing pin, plunger, working tool and switchgear.
The simplest scheme of hydraulic hammer represented in Scheme 1.
Scheme 1 –Scheme hydraulic breaker working
Viewed in my work hydraulic hammer mechanism is shown in Scheme 2.
Scheme 2 – Schematic diagram of the portable hydraulic impactor
The hydrohammer, which schematic diagram it is presented on the scheme 2 consists of the case 1 in which are coaxially placed a glass 12 and the drummer 2 forming with the case 1 camera of a forward stroke 5. The camera of reverse motion 6 is connected to the pressure head highway 18. The opening of a glass 10 connects the camera of a forward stroke 5 to the camera of a high pressure 7. Plunzher 4 has a ledge 14 for interaction with the camera of a forward stroke 5. The chamber 8 is connected with drain tenches 13.
4. Mathematical simulation of working process of hydraulic impactor Jackhammer
Designate working cameras of a hydrohammer as А,В,С,Е.
Find the pressure in all chambers:
где α1, α2, α3, – hydraulic resistance of the channel connecting the respective chambers.
Fuel Q determined the speed of piston-striker, plunger and cup:
где V1 – speed piston-striker,
V2 – speed of the plunger,
V3 – speed cup,
S– surface area in the respective chambers;
Spending equation in the respective chambers for piston-striker:
Spending equation in the respective chambers for a glass:
Spending equation in the respective chambers for plunger:
Balance equation costs:
The equation of motion of the striker has the form:
The equation of motion has the form of a glass:
The equation of motion of the plunger has the form:
Conclusion
The main objective of my future work is the analysis of the concept in order to select the most efficient methods for optimizing the design and operating parameters for hydraulic jackhammer by mathematical (simulation) modeling.
List of resources
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- Устименко Т.А. Обоснование структуры и выбор оптимальных параметров гидравлического отбойного молотка : дисс. … канд. техн. наук: 05.05.06 / Т.А.Устименко.–Донецк. 1990.–204с.
- Караев М.А. Гидравлика буровых насосов / М.А. Караев. – М.: Недра, 1983.-208 с
- Гидропневмоударные системы исполнительных органов горных и строительно-дорожных машин / А.С.Сагинов, А.Ф.Кичигин, А.Г.Лазуткин, И.А.Янцен. – М.: Машиностроение, 1980.-299с.
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