Abstract: A hydraulic system with a pressure source controllable via a load sensing signal, a pressure sink, at least two working sections, each having a hydraulic consumer and a control valve with a load sensing signal connection and at least one back-pressure valve arranged in a tank pipe between the control valve and the pressure sink. In such a system the pressure required from the pump in the neutral position must be as low as possible. On the other hand, however, oscillations should not occur, when an external force acts on another hydraulic consumer in the neutral position of a control valve. In the neutral position of the control valves the load sensing signal connection is therefore connected with the pressure sink via an auxiliary tank pipe by-passing the back-pressure valve.

Abstract: The heat exchanger comprises at least one heat-transfer wall which forms a separation between a hot primary fluid and a secondary fluid to be heated. Each heat-transfer wall is either a vertical cylinder having a cross-section in the form of a circle with a wavy profile in the case of a tubular heat exchanger or a vertical rectangular plate having wavy corrugations in the case of a plate-type exchanger, a series of assembled plates being intended to form leak-tight compartments for receiving primary fluid and secondary fluid in alternate succession. The secondary fluid is introduced into the upper end of the heat-transfer wall in the vicinity of the wave crests of the wall face which is directed towards the fluid.

Abstract: An air valve, in the snorkel leading to the air cleaner in the induction system of an internal combustion engine, is actuated by a vacuum operated servo controlled by the depression in the snorkel to maintain a constant depression at the air cleaner. An exhaust gas recirculation control valve, operated by the air valve control servo, opens proportional to air valve opening to control exhaust gas flow into the induction system proportional to exhaust back pressure and air valve opening thereby providing exhaust gas recirculation flow proportional to engine load.