Atlas Copco Aktiebolag

Voac Hydraulics Boras Ab

Orjan E Wennerbo

Bengt-Goran Persson

Bo Nilstam

Kyle G Martyn

A control means for a hydraulic motor connected to an external load comprises a directional valve (10) for selectively feeding hydraulic fluid to the motor from a pressure source and including load pressure sensing means (24, 25) connected to a load compensating valve (15) located upstream of the directional valve (10) for adjusting automatically the feed pressure in relation to the actual load pressure. The load compensating valve (15) includes a valve spindle (28) with opposite end surfaces (29, 30), one of which is exposed to the load pressure whereas the other is exposed to the feed pressure, and a selectively activatable feed pressure reducing means (38, 43; 50-57) for increasing the bias force acting on the load compensating valve spindle (28) in the closing direction of the latter in relation to the bias force acting in the closing direction of said valve spindle (28).

Control system for a hydraulic motor

A method for controlling a hydraulic motor with a hydraulic valve comprising an inlet section which includes a pump and tank connection and a maneuvering section having a slide (B1) and a load signal system (L1, L2, L3). The hydraulic valve also includes two regulating constrictions (S3, S4) which can be connected to and from a motor (C), such as a hydraulic piston-cylinder device. The maneuvering slide (B1) also includes a load level detecting constriction (S2) and a load signal drain (S5), and the pump generates an idling pressure. When maneuvering the maneuver slide (B1), the load signal Ps of the load signal system is increased by a further constriction (S1) located between the pump connection and that side of the load detecting constriction (S2) that has the higher pressure during the maneuvering process.

Method for controlling a hydraulic motor and a hydraulic valve therefor

Device in a hydraulic power system connected to a load driving hydraulic motor (18; 32), comprising a pilot controlled flow regulating directional valve (1; 29) for alternative connection of the service ports of the motor (18; 32) to a pressure medium source and a tank. The directional valve (1; 29) comprises two opposite and by a pilot pressure activatable activating means (3, 4), and a pilot pressure means (84) is arranged to pressurize and activate the activating means (3, 4), alternatively, and drain one of the activating means to the tank through a flow restriction (5, 7) at activation of the other activating means (3, 4). The power system comprises at least one control flow circuit (10-12; 72-83; 37-44) which communicates with one of the activating means (3, 4), and a valve means (11, 12; 71; 31) which is arranged to accomplish a flow through the control flow circuit (10-12; 72-83; 37-44) in relation to the load pressure on the motor such that the counter pressure from the flow restriction (5, 7) generates a compensating force in relation to the load pressure on the motor on the non-activated activating means (3, 4).

Pilot-operated flow controlling directional control valve with copying

A hydraulic drive system for one or more hydraulic motors, comprising a pump (1), a tank (25) for hydraulic fluid, one or more control valve sections (10, 11, 12) each being provided with a shunt passage and each being coupled to a respective hydraulic motor, a first shunt conduit (4) including the shunt passages of said control valve sections (10, 11, 12) connected in series for leading off of the tank (25) the temporarly surplus flow of hydraulic fluid from the pump (1), and a feed conduit (3) for connecting the control valve sections (10, 11, 12) in parallel to the pump (1). A second shunt conduit (5) is connected between the pump (1) and the tank (25) and includes a pressure responsive valve (6) which is arranged to operate in response to pressure in said first shunt conduit (4) downstream of a first non-variable restriction (13), and also in response to pressure in said shunt conduit (5) downstream of a second non-variable restriction ( 14), to establish a direct connection through said second shunt conduit (5) from the pump (1) to the tank (5) in relation to the size of the fluid flow in said first shunt conduit (4).

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Boras, Sweden

Orjan E Wennerbo