Hydraulic drilling machine

#This invention relates to a hydraulic drilling machine, especially a rock drill comprising a striking apparatus, a rotating motor and a feed motor, as well as pumps and valves necessary for their operation and control.

#French Pat. No 2,129,276 discloses a hydraulic drilling machine in which the striking apparatus is connected in series with the rotating motor of the drill, whereby increasing rotation resistance and pressure drop across the rotating motor decreases the power of the striking apparatus in order to avoid jamming of the drill steel. When starting to drill, as well as when drilling considerably nonhomogenous material, the function of this arrangement, however, does not serve the purpose. When the drill is rotating freely, or in a soft material, the striking force is at its maximum even if the striking and feed forces ought to be small in order to feed the drill slowly into contact with a hard material.

#In a drilling machine according to U.S. Pat. No. 3,979,944, this disadvantage has been eliminated by means of a suitable valve control. When using conventional valves it is not possible to accomplish a stepless control at reasonable cost.

#In the following, the invention will be more closely described by means of an example, with reference to the accompanying drawings in which:

#FIG. 1 is an elevational view of a drilling machine embodying the invention; and

#FIG. 2 is a schematic circuit diagram of a hydraulic drilling machine embodying the invention.

#FIG. 1 shows a conventional hydraulic drilling machine comprising a feed frame 20, rotatably mounted at the end of a supporting boom 21 which can be mounted e.g., on a chassis on wheels which is not shown in the drawings. The position of the frame 20 can be adjusted in relation to the supporting boom 21 by a hydraulic cylinder device 22. Mounted on a carriage 23 supported on the frame 20 are a hydraulic striking apparatus 15 and a rotary hydraulic motor 16 that turns a drill rod 24, at the end of which is a bit 25. The drill rod 24 is supported by a bearing 28 at the end of the feed frame 20.

#The carriage 23 is arranged to be movable e.g. by a chain 26 running over suitable, freely rotatable sprockets and over a driving sprocket 27 mounted on the output shaft of a hydraulic feed motor 17. The motor 17 feeds the drill rod 24 and drill bit 25 into a material such as rock or a vertical mine wall 29 in order to bore a hole into it. Hydraulic fluid is fed to the feed motor 17 through hydraulic lines 17a and 17c. The hydraulic fluid is fed to the striking apparatus 15 of the drilling machine and to the rotating motor 16 through hydraulic lines 15a and 16a, and it returns to tank R through hydraulic line 15c. The control and adjustment of the supply of hydraulic fluid takes place in a control center 30, which is more completely described below with reference to FIG. 2.

#The feed motor 17 and the rotating motor 16 of the drill are connected in series so that when the striking apparatus 15 is fed forward into the rock, the feed motor 17 receives its hydraulic pressure from the pump 14 and the rotating motor 16 receives hydraulic pressure from the outlet side of the feed motor 17. Further, the pressure of the liquid coming to the feed motor 17 is kept essentially constant by valve and coupling arrangements as will be described below.