A downhole tractor having a hydraulic system for driving a plurality of hydraulic cylinders and a plurality of hydraulic motors. The system comprises: a hydraulic power pack; a first hydraulic supply line for supplying hydraulic fluid to the plurality of hydraulic cylinders; a second hydraulic supply line for supplying hydraulic fluid to plurality of hydraulic motors; a valve section comprising a respective part of first hydraulic supply line and a further respective part of second hydraulic supply line, valve section further comprising an inlet for receiving hydraulic fluid, and a set of valves, and a hydraulic bypass supply line coupled to hydraulic power pack for supplying hydraulic fluid directly to the inlet of valve section bypassing at least part of first hydraulic supply line and second hydraulic supply line. The first and the second hydraulic supply line each comprise two parts connected via respective part in the valve section. Each respective part is connected to a respective sub-set of plurality of hydraulic components. The valve section configured for individually controlling flow of hydraulic fluid into each respective part of hydraulic supply lines.

A downhole tractor having a hydraulic system for driving a plurality of hydraulic cylinders and a plurality of hydraulic motors. The system comprises: a hydraulic power pack; a first hydraulic supply line for supplying hydraulic fluid to the plurality of hydraulic cylinders; a second hydraulic supply line for supplying hydraulic fluid to plurality of hydraulic motors; a valve section comprising a respective part of first hydraulic supply line and a further respective part of second hydraulic supply line, valve section further comprising an inlet for receiving hydraulic fluid, and a set of valves, and a hydraulic bypass supply line coupled to hydraulic power pack for supplying hydraulic fluid directly to the inlet of valve section bypassing at least part of first hydraulic supply line and second hydraulic supply line. The first and the second hydraulic supply line each comprise two parts connected via respective part in the valve section. Each respective part is connected to a respective sub-set of plurality of hydraulic components. The valve section configured for individually controlling flow of hydraulic fluid into each respective part of hydraulic supply lines.

Modular directional valve with two or more crossing elements (E1 . . . En) able, acting only on the entry side, to manage a variable displacement pump (PA) of the load sensing type. In particular, this management allows in a single drive, unlike the conventional crossing distributors, to make the flow rate to the utility independent of the load and allows setting a maximum flow rate at the end of the stroke; in multiple drives, it ensures that the sum of the required flow rates is independent of the loads. A compensated flow rate regulator is placed in the entry side so as to act only on the bypass line LC upstream of the first element (E1 . . . En) while a proportional choke is placed on the load line consisting of a 2-way 2-position tray.

According to an embodiment, a variable pressure device includes a channel constituting unit and a switch valve mechanism. The channel constituting unit constitutes a channel including a first regulator and second regulators that are arranged in series to the first regulator and are in parallel to one another. The switch valve mechanism selectively connects the second regulators to the first regulator. Opening areas of the second regulators are different from one another.

A device for selectively controlling the flow of hydraulic fluid through the pilot valve comprises a longitudinal axis (A) and a housing, an internal cavity, at least one inlet passage, at least one outlet passage, a guide disposed in the internal cavity, a first seat disposed in the internal cavity, a second seat disposed in the internal cavity, a movable blocking member disposed in the guide cavity, and an actuator configured to control the position of the movable blocking member.

A pressure control valve (1) includes a pressure port (P), a consumer port (A), a tank port (T), and a piston (K) which is displaceable counter to the force of a first spring (F1) and a second spring (F2). The springs (F1, F2) and area ratios of the pressure control valve (1) are designed such that the pressure port (P), in the non-pressurized condition, is connected to the consumer port (A) via an opening cross-section of the pressure control valve (1). An opening cross-section between the pressure port (P) and the consumer port (A) decreases depending on the pressure at the consumer port (A), and, upon attainment of a limiting pressure at the consumer port (A), the consumer port (A) is connected to the tank port (T). A related hydraulic system (HY) and a related motor vehicle transmission (G) are also provided.

According to an embodiment, a variable pressure device includes a channel constituting unit and a switch valve mechanism. The channel constituting unit constitutes a channel including a first regulator and second regulators that are arranged in series to the first regulator and are in parallel to one another. The switch valve mechanism selectively connects the second regulators to the first regulator. Opening areas of the second regulators are different from one another.

Modular directional valve with two or more crossing elements (E1 . . . En) able, acting only on the entry side, to manage a variable displacement pump (PA) of the load sensing type.

In particular, this management allows in a single drive, unlike the conventional crossing distributors, to make the flow rate to the utility independent of the load and allows setting a maximum flow rate at the end of the stroke; in multiple drives, it ensures that the sum of the required flow rates is independent of the loads.

A compensated flow rate regulator is placed in the entry side so as to act only on the bypass line LC upstream of the first element (E1 . . . En) while a proportional choke is placed on the load line consisting of a 2-way 2-position tray.

Hydraulic section (1) for use in a hydraulic distributor (10), comprising: a valve body (2); a main spool (3); pressure compensator (5) housed in a first hole in the valve body (2); a piston (11) housed in the first hole; an intermediate chamber (16) in fluid communication with the feed line (Pal), the intermediate chamber (16) extending at least partially in the first hole and being delimited by the rod (12) of the piston (11); two limiters (6, 7) and a drainage channel (18) pertaining to the intermediate chamber (16) for altering the pressure thereof and close the compensator (5).

A nose-wheel steering system is provided. The nose-wheel steering system includes a hydraulic motor including a drive shaft configured to rotate about a first axis; and a hydraulic motor start assist mechanism coupled to the hydraulic motor and configured to provide a temporary boost of hydraulic fluid pressure supplied to the hydraulic motor.