Patent GB-1468387-A (GB)
Title: Hyddraulically operated rotary percussive drilling apparatus
IPC: B25D9/12
Filed: 1974-11-07
Abstract: 1468387 Rotary-percussive rock drills SOC D'ETUDE ET DE CONSTRUCTION DE MACHINES POUR TOUTES INDUSTRIES 7 Nov 1974 [7 Nov 1973] 48290/74 Heading B3C [Also in Division B4] In a hydraulically operated rotary-percussive drilling apparatus such as a rock drill, the tool 1 is rotated by drive means, motor 4 gears 7-9, and is repeatedly struck by a hammer 2 in piston form slidably mounted in body 3, Fig. 1. A hydraulic distributer valve 18 controls the reciprocation of the piston 2 and is itself controlled by movements of the piston, the supply of hydraulic fluid to the valve being provided by a pump 37, Fig. 4, via lines 19, 19a. A feed thrust is applied to the body 3 by a ram 41 and means, i.e. sequence valve 49, sensitive to pressure changes in ram 41, adjusts the output of pump 37 by means of regulator 37a in dependence on the thrust applied so that the percussive energy will be increased when the thrust increases, e.g. on encountering hard rock. In the particular arrangement, shuttling of spool 25 of valve 18 connects and disconnects the supply of fluid to piston 2 which forms chambers 14, 16 with the body 3 of different cross-sectional area to provide different axial forces on the piston at the same pressure. Reciprocation of the piston opens and closes apertures 29 and 32 for controlling the supply of fluid to and from the valve 18. Alternative apertures 34 may be used to vary the strike frequency and stroke. Accumulators 22, 24, Fig. 1, alternate fluid vibration and maintain a substantially constant pressure in chamber 16. In Fig. 4, in addition to pump 37 for the strike means, similar variable output pumps 38 and 39 supply the rotary drill motor 4 and the thrust ram 41 respectively. These pumps are supplied with fluid by constant output pump 36 and all the pumps are rotated by shaft 40. The output of pump 39 is regulated by regulator 39a. In operation, the operator sets the drill rotation speed which is kept constant by means of valve 43, and the amount of thrust by means of valve 44 and ensures that flushing water for workpiece hole clearing flows along line 46. If the water pressure is insufficient sequence valve 48 prevents the water from passing to safety valve 45 which controls hydraulic fluid passing to thrust control valve 44 which in turn controls fluid passing to the ram so that it is automatically retracted. Providing the water pressure is adequate forward feed thrust commences and the tool 1 contacts the rock face. The increase of thrust pressure then arising is sensed by sequence valve 49 controlling strike-controlling valve 42 and fluid flows along line 19 to start the striking action in a "low strike" mode. Once the hole is started, the thrust pressure increases further and sequence valve 49 controls regulator 37a which increases the output of pump 37 to provide a higher energy "normal strike" mode. Regulator 37b keeps the pressure in pump 37 constant. Any increase in pressure at the intake of rotary motor 4 due to load changes is sensed by regulator 39a and this automatically reduces the thrust pressure so preventing stalling of motor 4.