Boring or penetrating the earth – Automatic control – Of advance or applied tool weight
Patent
1996-10-04
1998-07-14
Dang, Hoang C.
Boring or penetrating the earth
Automatic control
Of advance or applied tool weight
173 8, 173 11, 175122, E21B 4400
Patent
active
057789908
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an arrangement in a hydraulically operated rock drilling equipment, comprising a rock drill provided with a percussion device; a feed motor for feeding the rock drill in the drilling direction and back, respectively; a hydraulic pump; a percussion pressure line and a feed pressure line both connected to the pump for feeding hydraulic fluid to the percussion device and the feed motor, respectively; a return line from the percussion device and the feed motor for returning hydraulic fluid to a tank for hydraulic fluid; a feed regulation valve and a feed regulator for regulating the flow of hydraulic fluid to the feed motor, the feed regulation valve being a signal-controlled proportional valve and the feed regulator being connected to control the feed regulation valve by means of at least one feed regulation line.
In rock drilling, collaring a hole has to be performed by using set values lower than the normal set values used in drilling, such as percussion pressure and feed, until the hole formed in the surface of the rock is deep enough to ensure that the drill bit stays in the hole. This has usually been done in such a way that the driller adjusts set values for collaring manually and then turns the controls to their maximum position.
U.S. Pat. No. 4,074,771 discloses a solution where the feed pressure of the feed machinery is adjusted by means of a control lever operated by the driller. In this patent the percussion operation of the percussion machinery is arranged to be controlled by the pressure of the hydraulic fluid of the feed motor in such a way that when the pressure exceeds a predetermined lower limit, the feed of hydraulic fluid into the percussion machinery increases with increasing feed pressure. Correspondingly, the flow of hydraulic fluid into the percussion machinery decreases with decreasing feed pressure. Accordingly, the percussion power can be adjusted at the same time as the pressure of the feed machinery is adjusted by means of a control valve connected to the control lever. It is also known from the patent that normal drilling is switched on after collaring by pushing the control lever for feed pressure to its extreme position, whereby both the feed and the percussion will be set at maximum power. In this situation, the rotation and percussion machineries are connected to follow the pressure of the feed machinery in such a way that when the feed pressure decreases, the rotation power and the power of the percussion machinery also decrease.
The solution disclosed in the U.S. patent is very complicated and difficult to realize, in addition to which its use in drilling is not optimal from the driller's point of view. The simultaneous adjustment of the feed pressure and the power of the percussion machinery and the rotation motor causes problems and makes collaring more difficult.
The object of the present invention is to provide an arrangement for controlling a rock drilling equipment, which allows the driller to control the collaring easily and efficiently while also allowing efficient normal drilling. The arrangement according to the invention is characterized in that the arrangement further comprises a first pressure relief valve having a lower preset pressure value than the highest allowable operating pressure of the percussion device; a pressure difference valve in communication with the feed pressure line; and a signal-controlled control valve connected between the percussion pressure line and the first pressure relief valve on one hand and the pressure difference valve on the other hand and being controlled by the feed regulation line controlling the forward operation of the feed motor in such a way that when the value of the control signal of said feed regulation line is below a predetermined switching value, the first pressure relief valve is switched in communication with the percussion pressure line through the control valve and keeps the pressure of hydraulic fluid applied to the percussion device at said preset pressure value, and when the value of th
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Dang Hoang C.
Tamrock Oy
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