The invention relates to a control device for hydraulic power cylinders, in particular power cylinders of a road truck tailgate, comprising a hydraulic pump (1) driven by a motor (M). Said pump can be connected to a supply of medium and, via pump branch pipes, to a chamber of the operating cylinder (14) by means of allocated control valves (12,13). An adjustable electrical pressure gauge and switch unit (15-18) is connected to the chamber or corresponding pump branch pipe of the power cylinder. Said unit is fitted with a computer (15) for entering maximum pressure limits and used to stop the pump motor drive (2, 19) and activate a signal transmitter (20) when a preset maximum pressure is exceeded. In addition, a safety valve (22) set at a cut-in pressure lower than the preset maximum pressure is connected to the chamber or corresponding branch pipe (8",A,B) via an electromagnetic valve (23) which opens when the device is not operating.

An electric pump is turned ON and OFF by a main drive circuit including a negative pressure sensor for detecting a negative pressure in an accumulator, a first relay and a control device, and also turned ON and OFF by a back-up drive circuit including a negative pressure switch for detecting a negative pressure in an accumulator, and a second relay. For a period from the starting of the electric pump by the back-up drive circuit to the stopping of the electric pump by the main drive circuit, there is a period during which the electric pump is being driven only by the back-up drive circuit and a period during which the electric pump is being driven only by the main drive circuit. For each of these periods, a trouble of the main drive circuit and/or the back-up drive circuit can be determined by reference to a check signal indicative of the operational state of the electric pump. Thus, it is possible to reliably detect a trouble with the driving of the electric pump connected to the accumulator.

A brake system in which a hydraulic fluid can be conveyed from an accumulator via a valve into individual wheel brake cylinders, the hydraulic fluid being conveyed by a pump into the accumulator, having a pressure sensor arranged on the outlet side of the pump for detecting pressure pulsations in the hydraulic fluid arising in the operation of the pump and having an arrangement for evaluating the pressure pulsations in order to obtain a measuring signal for controlling and/or monitoring the pump.

A fuel delivery system for delivering fuel from a fuel tank to an internal combustion engine includes a fuel pump disposed within the tank and an accumulator communicating between the fuel pump and the engine for storing a volume of fuel under pressure. The system also includes a fuel pump control means for controlling the output of fuel flow from the fuel pump. The control means selectively causes the fuel pump output flow to either supply fuel to both the engine and the accumulator or bypass fuel at a lower pressure while fuel is supplied by the accumulator alone, thereby reducing the average power demand of the pump.

A control system 10 for monitoring operation of a high pressure plunger pump 12 includes a microprocessor-based controller 40 and a plurality of sensors. Inlet pressure transducers 48 output electrical signals to the controller at intervals of less than 1 millisecond, indicative of the instantaneous inlet pressure to the pump. The controller 40 shuts down pump operation if a number of instantaneous pressure signals within a selected time period exceeds a predetermined value, or if the average inlet pressure signal exceeds a preselected value. The control system 10 is substantially tamperproof, and stored data indicative of tampering, pump startup, pump shutdown, and pump alarm conditions are recorded in a memory for subsequent retrieval and analysis. The serial interface 82 allows communication between the system operating computer 68 and a setup/processing computer 84, which may optionally be remote from the control system by use of a modem.