Control valve for counterblow-tap hole-boring machine

A counterblow--tap hole--boring machine, especially for pneumatic rammer advance, combined with a counterblow device which serves as tapping equipment and a rotator for the actuation of a bar drill or a striking bar, consisting of sliding control valves which feed the main air to the consumer and back as exhaust, whereby an additional quick action ventilating valve quickly reduces the pressure of the used air, is provided with a mobile control piston (20) disposed on the distal end of the axially sliding control valve (15), which holds a valve disk (16) and controls the main air supply, between the housing (12) and the shaft of the sliding control valve (15), whereby a separate annular piston (18) alternatingly rests against the valve fitting surface (19) and a fitting surface (29) at the control piston (20).

This invention concerns a control valve for a counterblow--tap hole--boring 
machine, especially for pneumatic rammer advance, combined with a 
counterblow device which serves as tapping equipment and a rotator for the 
actuation of a bar drill or a striking bar, consisting of sliding control 
valves which feed the main air to the consumer and back as exhaust, 
whereby an additional quick action ventilating valve quickly reduces the 
pressure of the used air. 
A counterblow--tap hole--boring machine is used to open the mouth of a 
furnace on the structure of a blast furnace quickly and safely. 
It is common practice to use striking bars or a pneumatic hammer or a rock 
drilling machine for tapping a blast furnace, so the molten pig iron may 
flow out. One of the shortcomings of such rock drilling machines is that 
they only work in one direction. Loosening and pulling of the drilling bar 
still is dependent on manual work. For this reason counterblow boring 
machines have been used which in combination with a striking hammer also 
allowed pulling of the drilling bar with the help of pneumatic equipment. 
However, this improved tapping method still had the drawback that rotation 
during drilling was not possible and thus required a separate rotator. 
These units were attached on a mounting and automated with the help of 
control valves. Such valves naturally have one more shortcoming; when the 
striking hammer, the counterblow boring machine, respectively, are turned 
off some after-running due to the kinetic energy in the used air is 
inevitable. After-running may also be caused by faulty operation. This may 
have grave consequences if a striking hammer and a counterblow hammer work 
against each other. 
Based on this state of technology it is the purpose of this invention to 
eliminate after-running which occurs when switching from one consumer to 
the other, so they do not interfere with each other or destroy each other. 
In accordance with this invention this goal is achieved by a control valve 
equipped with a valve disk which can be moved axially and can close the 
main air supply, whereby a mobile control piston is disposed at the distal 
end of this control valve. In addition to this an annular piston valve 
alternatingly rests against the fitting surface of the valve and the 
fitting surface of the control piston. In this manner, the kinetic energy 
which remains when the valve is switched from one consumer to the other, 
i.e. the remaining used air which is still under pressure, can escape very 
quickly and thus prevents the two pistons or piston rods from striking 
against each other. 
This is particularly advantageous if the control valve is disposed at one 
end in the casing cap, if its distal end runs in the control piston and if 
its front side bears bore holes and a groove which are effectively 
connected to the annular area and the control channel. This allows the 
remaining control air to be evacuated through the control air channel. 
Furthermore, it is also advantageous if a spring is held in a groove in the 
front side of the sealing surfaces of the control piston and the annular 
piston. This keeps the two pistons from getting stuck (both of them are 
independent from gravity).

FIG. 1 shows a lateral view of a counterblow--tap hole--boring machine. A 
mounting is suspended on rollers (3) and roller bearings (4) from a 
carrier (1). whereby the base plate (2) can be moved in the longitudinal 
direction. Striking bar 5 extends from the counterblow gear (7) and may be 
equipped with various tools. Rotator 8 is engaged to striking bar 5 via a 
gear train. Striking gear 6 is connected to counterblow gear 7 via an 
intermediary part (9). The individual units are connected in air supply 
10, control valves 11 in particular. Striking gear 6 and counterblow gear 
7 form one unit, whereby the striking surface of the pistons affect each 
other via the rim of intermediary part 9. The energy of a blow is conveyed 
from the intermediary part and the tool mounted on the front end of it to 
the drill bar or striking bar (5). A rotator (8) is used for drilling and 
for loosening the tools. Its torque is conveyed to the intermediary part 
(9) by an external spline. Air for both striking gears (6, 7) and the 
rotator is supplied by a valve block, which consists of a number of valves 
(11). It is crucial that all necessary control pipes are integrated in the 
valve block, i.e. in the casing of valves 11. This is advantageous because 
it eliminates the time consuming task of sealing the pipes if the device 
needs to be disassembled. Such a drilling unit allows the establishment of 
a pilot drill with a hollow drill or a cutter, exchange of the drill bar 
for a striking bar, piercing, and pulling by means of counterblow gear 7. 
This helps to ensure shorter drilling time, longer tool life for the drill 
bit and the cutter, and prevents the striking bar from getting stuck in 
the mouth of the furnace. 
FIG. 2 shows a cross-section of a valve (11) whose housing (12) has a 
central bore which is closed with cap 13 and is sealed with ring gasket 
26. In housing 12 is a hollow (12a) which has a fitting surface (17, 19) 
on each end. From this hollow 12a a consumption channel (23) leads to 
connector flange 14 onto which more continuing pipes are connected. A seal 
is established through an axially sliding control valve (15) with a valve 
disk (16) which rests against fitting surface 17. Sliding control valve 15 
runs in a guide in cap 13 and is sealed with gasket ring 25, whereby the 
guiding area (30) and groove 15a house a spring (34). A channel which is 
disposed on the side of housing 12 serves as the main air channel (24) and 
is connected to the consumer channel (23) as long as valve disk 16 is in 
an open position. On the other end of housing 12 a control air channel 
(21) and a channel for used air (22) are disposed In the area of the 
control air channel (21), which runs along the side of housing 12, a 
control piston (20) is disposed. Gasket ring 27 establishes a seal toward 
the housing (12). There is also a pocket hole in the center which holds 
the axially sliding control valve (15), whereby the front side (32) is 
provided with some extra space and is sealed with the help of gasket ring 
25. On the upper end of the control piston (20) is a protrusion so a 
circular area (31) remains. There is also a bore (20a) in control piston 
20, which is connected to the circular area (31) via groove 20b. 
Furthermore, control piston 20 is provided with a fitting surface (29). 
Between valve fitting surface 19 and fitting surface 29 there is an area 
large enough to hold an annular piston (18) which can be shifted axially. 
It too is sealed with a gasket ring (25) against the shaft of sliding 
control valve 15. Channel 22 for used air is connected to this area. When 
no pressure applies control piston 20 and annular piston 18 are pressed 
apart from each other by spring 28. Control air enters circular area 31 
via control air channel 21, causing the control piston to move toward the 
end, lifting valve disk 16 of sliding control piston 15 from fitting 
surface 17. The main air channel is thus connected with the consumer 
channel (23). The consumers, striking gear 6, counterblow gear 7, and 
rotator 8, start to operate. The movement of control piston 20 is limited 
by annular piston 18, which causes it to be pressed against fitting 
surface 19 of the housing (12). This prevents escape of the used air via 
used air channel 22. At the same time control air reaches the front side 
(32) of sliding control valve 15 via circular area 31 and bore 20a, 
causing the sliding control valve to open completely. The movement of 
sliding control valve 15 is limited by protrusion 33 in cap 13. Now the 
valve is completely opened. In order to prevent the formation of an air 
pillow in guide area 30 an evacuation hole (35) is provided. 
When the force which presses against annular piston 18 via control piston 
20 is eliminated the remaining air from the consumer channel (23) can lift 
annular piston (18) from the valve fitting area (19) and escape via the 
used air channel. This ensures that a consumer stops very quickly and does 
not interfere with the consumer that works in the other direction. 
Another crucial feature is that a combination of two valves (11) allows the 
rotator (8) to reverse This is done in a fashion whereby one of the valves 
(11) is actuated and supplied with control air in the manner described 
above. The used air of rotator 8 is supplied to the other valve (11) via 
consumer channel 14. As the annular piston (18) is lifted the remaining 
pressure of the air flowing back can be released via used air channel 22. 
If the two valves (11) are supplied with control air in an alternating 
manner, a clockwise or counter-clockwise rotation can be achieved. This is 
of particular importance because no additional exhaust valve is necessary 
as the exhaust valve is integrated in the main air valve.