Design of Lubrication and Cooling Flushing Mechanism for Hand-

held Pneumatic Rock Drill

Yueyong Wang

1, 2, a

, Yimin Zhang

1, 2, b

, Zunling Du

1, 2

, Shijie Wang

School of Mechanical Engineering, Shenyang University of Technology, Shenyang, Liaoning 110870, China

Institute of Equipment Reliability, Shenyang University of Chemical Technology ,Shenyang, Liaoning 110142, China

Keywords: Pneumatic rock drill, lubrication mechanism, cooling flushing mechanism.

Abstract: The advantages and disadvantages of the traditional lubrication and cooling mechanism of Air-leg Rock

drill are analyzed. In order to solve the shortcomings of the traditional structure and the fatal disadvantages

of gas-water linkage failure and hammer washing, a new lubrication and cooling mechanism of Air-leg

Rock drill is designed. It prevents the backfilling of pneumatic rock drill in the normal working process and

at the end, improves the life of pneumatic rock drill as a whole, and has been verified in the customer site,

and achieved good results.

1 INTRODUCTION

Pneumatic rock drills used in mining, railway and

highway construction generally work in open pits,

tunnels or mountainous areas (Liu Enguo., 2013).

When the pneumatic rock drill works, there is

relative movement between the head and the rotating

sleeve and between the piston and the rotating nut. It

is easy to wear and tear (Chen Bingzhi, 1987).

Insufficient lubrication is one of the reasons that

often cause the failure of rock drill and parts damage

(Class B, Grade, 1979). Because of the change of

working condition of rock drill, water pressure also

changes, which can't guarantee that water pressure is

always lower than air pressure. In the water washing

mechanism of conventional pneumatic rock drill,

water pressure in water needle can't be adjusted.

Reverse irrigation during normal working process

and at the end of pneumatic rock drill will destroy

the lubrication system of pneumatic rock drill,

accelerate wear and tear, reduce the service life of

parts, and also reduce the machine torque. Drilling

efficiency decreases (Liu Jian, et.al, 2015).

2 CURRENT LUBRICATION

MECHANISM

Air leg rock drill needs lubricating oil for three

purposes: reducing friction, anti-corrosion and

sealing clearance. At present, pneumatic rock drill

has three parts that need lubrication (Yang

Wansheng, 2008): spline pair, brazing tail pair, head

and rotating sleeve matching pair. The lubrication

oil supply of pneumatic rock drill depends on the

exhaust of the front chamber of the cylinder, and the

residual air of compressed air containing atomized

oil passes through the friction pair parts mentioned

above. There are two ways of drainage (Cai Shumei,

2002):

One is the single drainage mode, and the

compressed air residual flow through the spline pair

gap, through a narrow way, flows through the

brazing tail pair and the head and the rotating sleeve

matching pair, leading to the atmosphere. It is

simple in structure, but when the rock drill is

operated under heavy load, because of less gas

flowing through and less atomized oil, it causes poor

lubrication and shortens the service life of the rock

drill.

The other is double drainage and compressed air

surplus through spline pair, which only leads to

brazing tail pair. In addition, a drainage air passage

is provided to lubricate the matching pair of the head

and the rotating sleeve. Its structure is complex and

the lubrication condition of the spline pair becomes

worse due to the reduction of compressed air surplus

flowing through the spline pair, which will also

shorten the service life of the rock drill.

172

Wang, Y., Zhang, Y., Du, Z. and Wang, S.

Design of Lubrication and Cooling Flushing Mechanism for Hand-held Pneumatic Rock Drill.

DOI: 10.5220/0008849001720174

In Proceedings of 5th International Conference on Vehicle, Mechanical and Electrical Engineering (ICVMEE 2019), pages 172-174

ISBN: 978-989-758-412-1

3 CURRENT COOLING AND

FLUSHING MECHANISM

In the working process of air leg rock drill, water

will supply water needle, through drill rod, to reach

the bottom of the hole, water will be used to cool

and wash the rock powder at the bottom of the hole

to achieve the purpose of dust and powder discharge

(Liu Guangwen, Wang Yueyong, Liu Enguo, 2018).

Ideally, when the Air-leg Rock drill works, the water

pressure of the water needle should be lower than

the air pressure. If the water pressure in the water

needle is higher than the air pressure, the water flow

will enter the air passage and cylinder block,

destroying the oil film of the moving parts, thus

affecting the normal work of the rock drill. When

the water pressure in the water needle is higher than

the air pressure, the water will be poured back into

the air channel. The water washing mechanism of

the existing pneumatic rock drill can not regulate the

water pressure in the water needle, and can not

guarantee that when the water pressure is higher

than the air pressure, the water pressure can be

regulated below the air pressure.

Therefore, there is a rigid requirement in the use

of air leg rock drill: the working pressure must be

lower than the working pressure. Excessive water

pressure can easily cause gas-water linkage (water

injection valve) failure; in particular, backfilling will

occur, which will cause air-water mixing to appear

"wash hammer" and destroy lubrication; there will

also be some disadvantages such as ice in silence

cover. The general water pressure is between 0.2

MPa and 0.3 MPa.

4 NEW DESIGN OF

LUBRICATION MECHANISM

In order to solve the above problems (Luo

Liangguang, 2008), a new design scheme of

lubrication mechanism is proposed.

The lubrication of the new air leg rock drill

consists of a control valve, a handle, a cylinder block,

a guide sleeve and a head (see Figure 1). The control

valve is arranged in the handle body. A strong blow

hole is opened on the control valve and a handle

hole is arranged on the handle body. In the position

of the strong blow hole of the control valve, an

annular groove is opened along the radial direction

of the control valve. When the pneumatic rock drill

enters the compressed air (oil), the compressed air

(oil) enters the nose of the pneumatic rock drill

through the annular groove of the control valve

along the handle channel, cylinder block channel,

guide sleeve channel and the nose hole. The width of

the annular groove is 2 mm and the depth of the

annular groove is 0.5 mm. After compressed air

(containing oil) enters the head, it passes through the

gap between the head and the rotating sleeve and

forms oil film to realize lubrication function. Then it

enters the body of the rotating sleeve through the

hole of the rotating sleeve, passes through the gap

between the rotating nut and the piston and forms oil

film to realize lubrication function. At the same time,

the gas forms a pressure chamber in the head, and

the pressure in the pressure chamber is higher than

the water pressure, thus preventing water from

drilling. The center hole of the rod is poured back

into the pneumatic rock drill.

Figure 1. New lubrication mechanism diagram.

5 NEW DESIGN OF COOLING

AND FLUSHING MECHANISM

The cooling and flushing mechanism of the air leg

rock drill (see figure 2) includes a water valve body

and a pressure regulating device that allows the

valve body to move to a fixed position to control the

opening and closing of water flow in the water

needle.

Figure 2. Drawing of New Cooling and Flushing

Mechanism.

The valve body contains a passage for opening

the valve at preset pressure and allowing water flow

to pass through; together with the valve, it can

prevent the water pressure in the needle from

Design of Lubrication and Cooling Flushing Mechanism for Hand-held Pneumatic Rock Drill

173

exceeding the preset pressure, and the valve can

open freely without pressure resistance.

The water valve contains a passage that allows

the water pressure in the water needle to enter the

other end of the valve. When the water pressure in

the water needle exceeds the preset pressure, the

water valve moves towards the closing direction,

controls the water flow into the water needle, and

adjusts the water pressure in the water needle.

A spring is placed at the other end of the valve,

which can drive the valve to move in the direction of

closure; the valve contains a passage that allows

water from the needle to enter the other end of the

valve, so that the valve closes before the pressure

exceeds the preset pressure to prevent the pressure

from exceeding the preset pressure. When the rock

drill stops working, the spring can push the water

valve to the closed state and stop the water supply.

6 APPLICATION OF NEW

INSTITUTIONS AND

CONCLUDING REMARKS

The new lubrication mechanism of pneumatic rock

drill improves the structure of control valve,

optimizes the strong blow and lubrication channel of

handle, cylinder block, guide sleeve and head, thus

effectively improves the lubrication effect of

pneumatic rock drill.

The new cooling and flushing mechanism of Air-

leg Rock drill can ensure that the water pressure in

the water needle is lower than the air pressure in the

working process of rock drill, prevent water from

backfilling into the body, destroy the oil film of

parts and components, and lead to corrosion or

abrasion of parts and components.

After the successful development of the above

two new mechanisms, they took the lead in the

application of S82 gas-leg rock drill. The first

prototype was tested in a metal mine (see Figure 3)

in Sichuan Province in 2017. The water pressure of

the mine is 0.2 MPa higher than that of the wind

pressure. The performance of the gas-leg rock drill

fully meets the design requirements, helping

customers to achieve rapid rock drilling, smooth

operation, shorter working hours, lower costs and

maximize the interests of customers. It is fully

recognized by customers.

Figure 3. Field tests.

REFERENCES

Cai Shumei. Lubrication mechanism for the head system

of a pneumatic rock drill [P]: China, 02243160.8.

2002-07-10.

Class B, Grade 75, Department of Foreign Languages,

Lanzhou University. Lubrication Theory and Practice

of Rock Drillers [J]. Pneumatic Tools for Rock

Drilling Machinery, 1979 (03), 27-34.

Liu Enguo. A Brief Analysis of the Development Trend of

Pneumatic Rock Drilling Machinery [J]. Pneumatic

Tools for Rock Drilling Machinery, Phase 4, 2013: 14-

16.

Liu Guangwen, Wang Yueyong, Liu Enguo. Research on

water washing mechanism of pneumatic rock drill [J].

Pneumatic tools for rock drilling machinery, No. 3,

2018: 37-39.

Liu Jian, Wang Yueyong. Lubrication and cooling

mechanism of a pneumatic rock drill [P]: China,

201520300855.6. 2015-05-12.

Luo Liangguang. Conception and Practice of New

Generation Energy-saving and Environmental-friendly

Rock Driller [J]. Pneumatic Tools for Rock Drilling

Machinery, 2008 (1), 4.

Translated by Chen Bingzhi. Durability of rock drilling

machinery and determination of accuracy of matching

parts [J]. Pneumatic tools for rock drilling machinery,

1987 (2), 47.

Yang Wansheng. Factors affecting the life of pneumatic

rock drills [J]. Pneumatic tools for rock drilling

machinery, Phase 2, 2008: 18-21.

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