Patent ID: 6983926

Claim:
A check valve arrangement for a hydraulic consumer which permits connecting a consumer line of the hydraulic consumer selectively to a medium pressure line or a high pressure line, said check valve arrangement comprising a check valve having a housing which is connected to at least one medium pressure line, a high pressure line, and the consumer line, a piston slideably mounted in said housing for selective movement between a flow position wherein the medium pressure line and the consumer line are connected and the connection between the high pressure line and the consumer line is blocked, and a blocking position wherein the connection between the medium pressure line and the consumer line is blocked and the connection between the high pressure line and the consumer line is opened, only when a predetermined hydraulic limit pressure is present in the consumer line, wherein the piston is constantly biased toward its flow position by the pressure in a second medium pressure line which is connected to the valve housing, and wherein the piston reaches its blocking position only under a pilot load provided by the high pressure line and an additional pilot load provided by said predetermined hydraulic limit pressure being present in the consumer line, wherein the piston has on its circumference two counteracting differential surfaces, with one of the surfaces communicating with the second medium pressure line, and with a second of the surfaces communicating with the high pressure line, and wherein the piston further includes a consumer pressure surface which communicates with the consumer line and is operative to bias the piston toward the blocking position.