Hydraulic lifting device for vertically moving the roof of a commercial vehicle

Abstract

Hydraulic lifting device (16*, 16**) for vertically moving a roof (4) of a commercial vehicle (1), which includes a pumping device (21) with two pumps (23, 29) and a tank (44) for a hydraulic fluid, wherein the two pumps (23, 29) can be operated manually by means of only one operating lever (22) and can draw hydraulic fluid from the tank (44) via at least one suction line (24, 30, 50), wherein in at least one suction line (24, 30, 50) a check valve (25, 31, 51) opening in the direction of the pump (23, 29) is arranged, wherein the first pump (23) is connected on the output side to a first delivery line (26) and the second pump (29) is connected on the output side to a second delivery line (32), wherein the second delivery line (32) is connected to the latter via a further check valve (34) opening in the direction of the first delivery line (26), wherein a check valve (27) is arranged in the first delivery line (26), which closes the first delivery line (26) in the direction of at least one pump (23, 29), wherein the first delivery line (26) is connected to a pressure chamber (45) of a piston-cylinder arrangement (28), wherein the second delivery line (32) is connected to a first pressure relief line (33) which is connected to a first pressure relief valve (35), wherein the first pressure relief valve (35) is connected on the outlet side to a return line (36) which leads into the tank (44), wherein between the first delivery line (26) and the first pressure relief line (33) the further check valve (34) which closes in the direction of the first pressure relief valve (35) is arranged, wherein the first delivery line (26) between the check valve (27) located there and the pressure chamber (45) of the piston-cylinder arrangement (28) is connected to a return line (41), which is connected via a manually operated check valve (42) to a return line (43) opening into the tank (44), and in which the pumping device (21) can be operated in two delivery performance levels, for which means are available which effect an automatic switching of the delivery rate of the pump device (21) from a higher delivery rate to a lower delivery rate per actuation of the actuating lever (22), characterized by that the pressure of the hydraulic fluid prevailing in the pressure chamber (45) of the piston-cylinder arrangement (28) can be supplied to the control pressure input of the first pressure relief valve (35) via a switching pressure line (37), and that the first delivery line (26) between the second check valve (27) located there and the first pump (23) is connected via a second pressure relief line (38) to a second pressure relief valve (39), the outlet of which is connected to the tank (44) via a return line (40).

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