Abstract: An advancing assembly for underground powered shield support having at least one floor skid for supporting the powered shield support, an advancing beam and a substantially perpendicularly arranged lift cylinder for lifting the floor skid relative to the advancing beam during an advancing movement. The lift cylinder has a cylinder foot supported above the advancing beam and a cylinder head buttressed on a bridge and hydraulically displaceable relative to the cylinder foot. In order to improve a powered shield support and in particular the advancing assembly of a powered shield support, the lift cylinder is a double lift cylinder having a first cylinder stage, comprising the cylinder head, and a second cylinder stage, wherein a compression spring is arranged between the cylinder stages.

Abstract: A hydraulic shield support is disclosed with at least two adjustable-length hydraulic props supporting a dedicated shield, which are connected through a control bank to a hydraulic fluid supply and borne on base shoes, and to which a pressure in excess of the pressure of the hydraulic fluid may be applied in the set condition of the shield support. In order to provide almost any pressure level at each shield support at a deep face in a simple way, the shield support has at least one pressure intensifier located in a hydraulic pipe system between the hydraulic fluid supply and the hydraulic props, with an oscillating intensifier piston in the form a differential piston effecting the increase in pressure. The low pressure inlet of the pressure intensifier is connected to the setting pressure pipes upstream, and its high-pressure outlet downstream, of a hydraulically-releasable non-return valve.

Abstract: A lift cylinder arrangement is disclosed for a hydraulic support frame for underground mining. The support frame has a lift cylinder for lifting the base shoes during advancing, which is supported on the one hand on a return rod and on the other hand, in a pivoting manner, with an end supporting head to a drawbar connected to the base shoes. In order to allow a simple, rapid and reliable connection between the supporting head and the drawbar, the supporting head is connected to the drawbar by a plug-type locking system comprising two plug-type locking elements, which include first locking notches on the drawbar, and arranged complementarily thereto second locking notches on the supporting head, whereby the plug-type locking elements engage in at least one of the locking notches with clearance.

Abstract: A hydraulic shield support is disclosed with at least two adjustable-length hydraulic props supporting a dedicated shield, which are connected through a control bank to a hydraulic fluid supply and borne on base shoes, and to which a pressure in excess of the pressure of the hydraulic fluid may be applied in the set condition of the shield support. In order to provide almost any pressure level at each shield support at a deep face in a simple way, the shield support has at least one pressure intensifier located in a hydraulic pipe system between the hydraulic fluid supply and the hydraulic props, with an oscillating intensifier piston in the form a differential piston effecting the increase in pressure. The low pressure inlet of the pressure intensifier is connected to the setting pressure pipes upstream, and its high-pressure outlet downstream, of a hydraulically-releasable non-return valve.

Abstract: A lift cylinder arrangement is disclosed for a hydraulic support frame for underground mining. The support frame has a lift cylinder for lifting the base shoes during advancing, which is supported on the one hand on a return rod and on the other hand, in a pivoting manner, with an end supporting head to a drawbar connected to the base shoes. In order to allow a simple, rapid and reliable connection between the supporting head and the drawbar, the supporting head is connected to the drawbar by a plug-type locking system comprising two plug-type locking elements, which include first locking notches on the drawbar, and arranged complementarily thereto second locking notches on the supporting head, whereby the plug-type locking elements engage in at least one of the locking notches with clearance.

Abstract: A hydraulic cylinder (10), especially as a pit prop or moving cylinder unit in underground mining, with a locking ring (16) arranged on an outer cylinder tube (11) sealing it at its end with a lead through for an axially movable rod element (12; 13) accommodated in it. The locking ring (16) is provided in the lead through surrounding the rod element (12; 13) with a sealing arrangement (22) resting on the outer side (34) of the rod element (12; 13). The sealing arrangement (22) has a guide ring (29) provided with grease grooves (33) open to the outer side (34) of the rod element (12, 13), which can, be supplied with lubricant for the grease grooves (33) via a lubricant line (35) accessible on the outside on the hydraulic cylinder (10) and which is arranged in an accepting groove (40) formed interlocking ring (16) between an axially inner and an axially outer collar (38; 39).

Abstract: A hydraulic cylinder (10), especially as a pit prop or moving cylinder unit in underground mining, with a locking ring (16) arranged on an outer cylinder tube (11) sealing it at its end with a lead through for an axially movable rod element (12; 13) accommodated in it. The locking ring (16) is provided In the lead through surrounding the rod element (12; 13) with a sealing arrangement (22) resting on the outer side (34) of the rod element (12; 13). The sealing arrangement (22) has a guide ring (29) provided with grease grooves (33) open to the outer side (34) of the rod element (12, 13) which can be supplied with lubricant for the grease grooves (33) via a lubricant line (35) accessible on the outside on the hydraulic cylinder (10) and which is arranged in an accepting groove (40) formed interlocking ring (16) between an axially inner and an axially outer collar (38; 39).

Abstract: The double telescopic prop comprises an outer cylindrical casing tube 1, an inner tube 2 which is displaceable therein and a piston rod 3 which can be extended therefrom. The hydraulic fluid for extending the two prop stages is conveyed through a connection 14 to the piston 5 of the inner tube 2 and is conveyed via a bottom valve to the piston 7 of the piston rod 3. The prop is retracted if hydraulic fluid flows via the connection 17 into the outer annulus 11 between the cylindrical casing tube 1 and the inner tube 2. A size ratio of 8.8:1 at most, which is favourable for the retraction of the prop, exists between the area of the inner tube 2 and the ring area of the annulus 11.