FIELD OF THE INVENTION

The invention relates to machinery used in mining for crushing ore and rocks. The device can be used for crushing shingle of screened gravel in a gravel pit. BACKGROUND OF THE INVENTION

Three types of crushers are mainly used for crushing rocks - jaw crushers, cone crushers and impact crushers.

As a rule, jaw crushers are used as primary crushers to crush large rocks into smaller fractions in a quarry; however, a jaw crusher would not provide the final and preferred (cubic shape) particle shape to the material that is being crushed (crushed stone).

Impact crushers are used for crushing materials from demolished buildings at construction sites,as well as for manufacturing ore and rock products (crushed stone) in quarries. Impact crushers cannot be used for crushing large rocks that are highly abrasive and, as the rocks are deformed during high speed processing, they create finer material than jaw crushers or cone crushers.

Cone crushers are mainly used as secondary crushers. Cone crushers are used for crushing material that has already been processed or has a natural fraction that allows it to be fed straight into a crusher. Cone crushers process ores into smaller fractions and provide the final shape for the processed material (crushed stone particles).

Acone crusher operates on the principle of feeding source material from the above into the crushing chamber where it will start to sink downwards due to gravity and the eccentric gyration of the cone. At the lower end, the space between the cone and the concavesbecomes narrowerand the source material is therefore crushed into increasingly smaller fractions. The lower end of the cone is equipped with a flange giving the ore particles their final shape. An adjustable opening determines the largest possible size of the particle of a product.

The above three types of crushers are also used in combination; in this case, the crushers form a so-called enrichment complex. As a rule, a jaw crusher and a cone crusher are used sequentially. The processing capacity and mining characteristics also determine whether the enrichment complex is stationary, semi-mobile or mobile.

Mobile crushers are usually mounted on chassis with pneumatic tyres or on frames with tracks which ensure that it is possible to move and transfer the machines easily. Mobile crushers are used in quarries with smaller production outputs; however, more and more mobile crushers with increased production capacities and larger dimensions are being produced. The greatest advantage of mobile machinery is that they can be transported from one production site to another (from one quarry to the next) at a small cost compared to stationary and semi-mobile crushing units. However, the dimensions and capacity of mobile machinery are limited by the parameters and weight of vehicles that can legally be moved on carriage ways. Hence, mobile crushers are suitable for quarries where production outputs are smaller and in situations where the machines have to be constantly transported from one production site to the next (different construction sites, contract work for smaller quarries). The technical solution that resembles this invention the most is the Sandvik UD 210 mobile crushing plant

(¾tfo://www.miningandconstruction.sandvfc

dex/babOfO 13b0b8d 1 c6c 12574210044d2d 1 /SFILE/UD210%20spec.pdf) downloaded on 18.09.2013. This device has a jaw crusher, a cone crusher and a 3 deck screener mounted on a single frame. The jaw crusher (primary crusher) crushes ore into smaller fraction. From the jaw crusher, material will move to the first screener deck. Crushed ore with a particle size that is smaller than the holes in the first screener deck will fall through and will be immediately screened into up to three different fractions. Material that was not broken down into sufficiently tiny fractions after primary crushing will move across the first screening deck into the cone crusher which crushes the ore into smaller particles and gives the ore its final particle shape. Output material from the cone crusher is transported back to the 3 deck screener by a conveyor; after it is re-fractioned, it will be transported to a heap by several conveyors as a finished product.

The main disadvantage of the above mobile crusher is that two of its units (crushers) are fed through a single hopper, meaning that ungraded material can enter the jaw crusher. A repeated crushing of larger boulders creates finer material and requires more energy. As the machine has only one hopper, a prior grading of the source material would not improve matters because separately graded material cannot be fed to the crushers. Jaw crushers cannot be used for crushing very fine source material because the adjustment minimum of the bottom opening of the two jaws is limited. Smaller particles will pass through the jaw crusher without even being deformed.

SUMMARY OF THE INVENTION

The aim of the invention is to eliminate the previously described deficiencies. For this purpose, a device is provided for producing crushed stone that directs the source material (shingle) through several different hoppers to the crushers, thus directing ore of the correct size into a specially adjusted cone crusher. The selective delivery of source material and the correct adjustment of cone crushers ensure a better quality of the product (crushed stone), create less screenings and allowusingfiner shingle.

The object of the invention is a mobile gravel crusher consisting of a mobile frame fitted with two or more independently functioning cone crushers, each of which has been adjusted to crush previously screened shingle in the desired size, whereas a separate hopper is located above each cone crusher that is equipped with a vibrating feeder and below each cone crusher is a belt conveyor for transporting crushed material (crushed stone) away from the openings of the cone crushers. The device also comprises a control and electric motors for operating the vibrating feeders, cone crushers and belt conveyors either separately or simultaneously.

Feeding several cone crushers separately is necessary for ensuring that eachspecifically adjusted cone crusher would receive shingle in a size that would guarantee an excellent quality of the end product, increased productivity of the device, cause fewer screenings and would allow utilizing shingleof smaller sizes.

In order to obtain predetermined fractions, quantities and the desired grading of crushed stone, the feed rate of shingle loaded into the hoppers is adjustable with vibrating feeders.

In addition to adjusting the speed of the feeders of hoppers, it is possible to change the grading of the produced crushed stone by adjusting the rotation speed of each cone crusher, which in turn helps improve the quality of the end product (crushed stone). The content of fractions in the crushed stonecan be adjusted by adjusting the speed of each belt conveyor separately.

The device can be used in gravel pits for crushing the shingle of screened gravel. Gravel is a mineral resource containing 35% or more particles larger that 5 mm (Regulation no 29 of the Minister of the Environment from 21.04.2005). Only shingle contained in gravel is used to producecrushed gravel. In gravel pits, the raw material for producing crushed stoneis not dynamited from rock deposits; instead, it is screened from the rest of the materials.

The quality of crushed gravel depends on the grading of the material, the shape of the crushed stone particles, the amount of particles with rounded surfaces in the final product and the physical parameters of the shingle (compressive strength, cold resistance, etc.). One of the main problems with producing crushed stonefrom gravel is that the content of shingle in the overall amount of the material is low and the size of shingle is small. This causes low productivity in producing crushed stone and low quality of the product because a large amount of gravel has to be screenedto produce a sufficient quantity of raw material (shingle) and finer shingle hinders the production of crushed stone with the desired quality.

The use of the mobile gravel crusher of the present invention permits solving the above problems of producing crushed stone and to guarantee high quality of the crushed stone.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 Technical drawing of the mobile gravel crusher

Figure 2 Side view of the mobile gravel crusher

Figure 3 End view of the mobile gravel crusher

Figure 4 Mobile gravel crusher in its working position

DESCRIPTION OF THE PREFERRED EMBODIMENT

The mobile gravel crusher comprises a mobile frame on which several and preferably three independent cone crushers operate (2A, 2B, 2C), each of which has been adjusted to crush previously screened shingle in predetermined sizes. A separate hopper (3A, 3B, 3C) and a vibrating feeder (4A, 4B, 4C) is located above each cone crusher; a belt conveyor (5A, 5B, 5C) is located below each cone crusher (2A, 2B, 2C). The device comprises electric motors (6A, 6B and 6C) for operating the vibrating feeders, electric motors (7 A, 7B and 7C) for operating the cone crushers, electric motors (9A, 9B, 9C) for operating the belt conveyors (5 A, 5B, 5C), and a control panel (8) for controlling the work of the electric motors.

Below, the operation of the mobile gravel crusher has been explained based on producing predetermined fractions of crushed gravel (preferred embodiment).

In a quarry, gravel is screened into shingle in the following fractions:

- 8 to 16 mm fraction (shingle A)

- 16 to 32 mm fraction (shingle B)

- 32 to 64 mm fraction (shingle C)

Shingle previously screened into fractions is fed into the hoppers of the mobile gravel crusher by a wheel loader (Fig. 4) as follows:

- Shingle A is loaded into the hopper 3A.

- Shingle B is loaded into the hopper 3B.

- Shingle C is loaded into the hopper 3C. Hoppers guide the shingle into different cone crushers through vibrating feeders (4A, 4B, 4C). The rate of delivery of the material (speed of the feeders) can be adjusted on the control panel 8 that can be used for adjusting the speed of electric motors 6A,6B, 6C.

Shingle is fed into the cone crushers as follows:

- The vibrating feeder 3 A feeds the cone crusher 2 A.

- The vibrating feeder 3B feeds the cone crusher 2B.

- The vibrating feeder 3C feeds the cone crusher 2C.

Each cone crusher produces shingle in a predetermined and optimum particle size. In order to achieve the best results, the operating components of the cone crushers (opening between the cone and concaves) are adjusted as follows:

- cone crusher 2 A with an opening of 10 to 15 mm

- cone crusher 2B with an opening of 18 to 23 mm

- cone crusher 2C with an opening of 35 to 40 mm

Cone crushers are adjusted to produce crushed stone in the following fractions:

- The cone crusher 2A produces fractions of 0 to 8 mm (main fraction is 4 to 8 mm). - The cone crusher 2B produces fractionsof 0 to 16 mm (main fraction is 8 to 16 mm).

- The cone crusher 2C produces fractions of 0 to 32 mm (main fraction is 16 to 32 mm).

The productivity of the cone crushers (rotation speed) can be changed from control panel 8 which is used to adjust the speed of the electric motors 7 A, 7B, 7C of the cone crushers.

Material falls from the cone crushers onto the belt conveyors 5A, 5B, 5C.

The processed material falls onto the belt conveyors as follows:

- Product falls through the cone crusher 2A onto the belt conveyor 5A.

- Product falls through the cone crusher 2B onto the belt conveyor 5B.

- Product falls through the cone crusher 2C onto the belt conveyor 5C.

Belt conveyors transport the crushed stone away from the cone crushers and load it into a heap with the help of a swivel conveyor located next to the machine. The speed of all belt conveyors can be changed with the electric motors (9 A, 9C, 9B); the control panel 8 enables adjusting their rotation speed.

The mobile gravel crusher ensures excellent quality indicators due to the characteristics of its technical design.

The end product (crushed stone) is guaranteed to have a larger content of crushed particles and a better flakiness and elongation index. This result is achieved by feeding shingle with specific diameters based on the diameters of previously screened shingle into each hopper which are fed into a cone crusher that has been specially adjusted according to the diameter of the shingle. Therefore, the mobile gravel crusher also allows utilizingfiner shingle.

As it is possible to adjust the opening of each cone crusher (the distance between the cone and the concaves) to an optimum size, the process creates less fine material, making it possible to produce crushed stone with the best grading (optimum grading). The possibility of adjusting the feed rate of the material to the hopper and the rotation speed of each cone crusher (including stopping the operation if necessary) allows adjusting the grading of the end product (including the particle size of the intermediate screen). Several belt conveyors that can be adjusted separately collect the material and transport itfrom the cone crushers to a heap. The possibility to adjust the operational speed of belt conveyors also helps to adjust the grading of the end product (including the particle size of the intermediate screen).

The use of the mobile gravel crusher simplifies the possibilities of utilizing local mineral resources (gravel) and ensures excellent quality and yield of the product (crushed gravel).