Abstract: In order to increase the delivery pressure of the reciprocating pump-actuating mechanism of hydraulic feed pumps having a high pumping capacity, stacks of thin spacer discs are provided on either side of a sealing ring sealingly engaged in a sealing position between the plunger and the cylindrical bushing, said stacks of spacer discs being axially movable along the plunger in the normal non-sealing position. A pressure-distributing bushing is disposed between the stack of spacer discs which faces the free end face of the plunger and the sealing ring, said pressure-distributing bushing rapidly compensating the pressure between said stack of spacer discs and the end face of the pressure-distributing bushing facing the sealing ring.

Abstract: A process is disclosed for cutting rock by means of discharging a medium under high pressure from a nozzle head at a fixed oscillating angle. A nozzle head on the end of the pressure hose is set in a freely pulsating movement through the discharge of a medium under high pressure. The movement of the nozzle head is controlled by a guide with stops. An apparatus for carrying out this process is also disclosed. The apparatus comprises a suitable nozzle head on a delivery line 1 for discharging a medium under high pressure and with a fixed oscillating angle and a guide 6 with stops 4. A flexible high-pressure hose is used as the delivery line 1.