Abstract: The invention concerns a hermetic cooling compressor with an electric motor having a variable speed controlled by a converter cooled by a cooling medium flow. The compressor and the converter are formed together as a unit, in which a medium flowing through the unit is used for cooling of the electronic circuit of the converter. Thus the electronic circuit can be made without bulky cooling plates.

Abstract: A method for the field-oriented control of an induction motor (2) by means of a frequency converter (1) is disclosed, in which method a transformation angle (.delta.) is determined by estimation and is corrected in dependence on a rotational speed (.omega..sub.mR) of a rotor flux vector (i.sub.mR) or of the induction motor (2) and/or in dependence on a delay time (T.sub.del). In this connection it is desirable to improve the control behavior. To that end, the transformation angle (.delta.) is corrected a second time to compensate for a phase shift in the frequency converter (1).

Abstract: Method for commutation of a brushless motor being supplied with electrical energy from a DC intermediary circuit via a multi-phase inverter, by which a first current and a second current value are determined and the length of a commutation interval is set in dependence of these current values. With motors being exposed to heavily varying load torques during one rotation, e.g. motors driving a compressor, a stable operation must be reached. For this purpose a correction value is added to the pre-set commutation interval determined by the speed of the motor, said correction value being the result of the difference of the actual value of the intermediary circuit current and a filtered and delayed value of the intermediary circuit current, multiplied by a weighting factor.

Abstract: A hydraulic vane machine has a rotor, in which several vanes are arranged radially movable, and a stator having a stator bore, whose wall is made as a guiding contour on which the vanes bear. It is intended to prolong the life of such a machine, even when the machine is operated with a poorly lubricating hydraulic fluid, such as water. For this purpose at least one vane has a wearing surface on the end bearing on the guiding contour. Further, a channel arrangement is provided between high pressure and low pressure sides of the vane, which channel is blocked as long as the wearing surface has a predetermined thickness, and opened when the wearing surface is thinner than the predetermined thickness.

Abstract: In a method for controlling the superheat temperature (T.sub.u) of the refrigerant in an evaporator arrangement (1) of a refrigeration system or heat pump system (1-4), the evaporator arrangement (1), a compressor arrangement (2), a condenser and a controllable expansion valve (4) are arranged in succession in a closed circuit. The superheat temperature (T.sub.u) is controlled in dependence on a comparison between desired and actual values. The desired value (W.sub.2) of the superheat temperature (T.sub.u is varied automatically in dependence on the difference (d) from a reference value (W.sub.1) of a periodically determined function (S) of a number of sampled values of a temperature (T.sub.1 ; T.sub.2) of the refrigerant with the aim of a stable control of the superheat temperature (T.sub.u). To achieve optimum filling and to optimize the superheating in such systems, provision is made for the said function (S) to characterize the variability of a number of sampled values of the temperature (T.sub.

Abstract: A hydraulic control device is disclosed, having a pressure connection and a tank connection and having a metering pump unit (4) that comprises at least two metering pumps (5, 6) connected hydraulically in parallel and operable mechanically in parallel and also a cut-off valve (8) in hydraulic connection between the two metering pumps (5, 6), the cut-off valve (8) being flange-mounted on a metering pump (6) and having in a housing (13) a slider member (12) which, under pressure form the pressure connection (P), is movable axially towards the metering pump (6). It is desirable to keep wear and tear to a low level such a control device. For that purpose, a displacement-limiting device (26, 28) for the slider member (12) is provided, which prevents the slider member from bearing on the metering pump (6).

Abstract: A process for controlling a refrigeration system, as well as the refrigeration system and a new expansion valve for the refrigeration system. An electronic regulator is used to operate a sensor system having a device for applying heat power to the sensor system in direct dependence on sensed superheat of the refrigerant leaving the evaporator. By locating the sensing system in communication with liquid refrigerant upstream of the evaporator, heat transfer to the liquid refrigerant is utilized for operation of the sensor system rather than heat transfer to the superheat, resulting in a far more stable and efficient refrigeration control.

Abstract: A refrigeration system having a plurality of cooled surfaces, each of which has a thermostatically controlled refrigerant supply valve. The valves are pulse-width modulated, each having the same period and being so controlled so they have staggered openings relative to one another thus providing a more uniform load on the system.

Abstract: A hydraulic axial piston machine (1) is disclosed, having a cylinder drum (3) with at least one cylinder (4), in which a piston (5) is arranged to move back and forth, which piston bears by way of a slider shoe (7) against a swash plate (8), wherein a pressure plate (9) is provided which holds the slider shoe (7) in contact with the swash plate (8) and is supported against the cylinder drum (3) by way of a ball-and-socket joint (10) comprising a ball-like body (12) and a counterpart (13). In such an arrangement, one would like to avoid weakening the pressure plate by the ball-and-socket joint. To that end, a part of the ball-and-socket joint (10) is provided with a supporting surface (17) which extends substantially parallel to the surface of the pressure plate (9) and by means of which this element (12) lies in face-to-face contact with the pressure plate (9).

Abstract: A hydraulic valve with a housing, which is made of a plastic material, and with at least two fluid connections and a valve element arranged movably in the housing. A valve of this kind must on the one hand be able to withstand a sufficient pressure and on the other hand the production of the valve must be inexpensive. For this purpose the housing is surrounded by a metal sheet enclosure having at each fluid connection an opening, which is surrounded by a metal sheet wall projecting from and connected with the metal sheet enclosure.

Abstract: A valve is disclosed having a closure member which co-operates with a valve seat and is movable by an actuating device with a driver element, which driver element is guided in a housing. It is desirable for such a valve to operate reliably and have a long service life. For that purpose, a high-temperature thermoplast is arranged between the housing and the driver element.

Abstract: An enclosure for a transmitter, particularly a pressure transmitter, comprising an upper part containing connection terminals and an outer enclosure connected with the upper part. A printed circuit board is mounted in the chamber formed by the upper part and the outer enclosure. To increase the immunity of the pressure transmitter from electrical noise, an inner conducting cylinder is used, the cylinder being fixed by a pressure fitting with the outer enclosure. At the same time stampings in the inner cylinder fix the printed circuit board and create earth connection from the printed circuit board via the inner cylinder to the outer enclosure. Besides improving the noise immunity, the invention simplifies assembly of the transmitter and increases mechanical strength, including resistance towards turning and tilting torques.

Abstract: A three-way or multi-way valve is provided, which is built up of a plurality of two-way valves, each of which has a high pressure connection and a low pressure connection which are separated from each other by means of a valve seat with which a closure element co-operates, the two-way valves being arranged to be operated in pairs or in groups by means of a control pressure fluid by way of a control pressure line opening into a pressure chamber, and one of the two-way valves of each group being arranged in a connection between a pressure source and a load, and another two-way valve of the same groups being arranged in a connection between the load and a pressure sink. With a valve of this type, it is desired to obtain improved closing behavior with simple construction. For this purpose, at least one of the connections, especially the high pressure connection, of at least one valve of each group communicates with the control pressure line by way of a throttle channel.

Abstract: A process for controlling a refrigeration system, as well as the refrigeration system and a new expansion valve for the refrigeration system. An electronic regulator is used to operate a sensor system having a device for applying heat power to the sensor system in direct dependence on sensed superheat of the refrigerant leaving the evaporator. By locating the sensing system in communication with liquid refrigerant upstream of the evaporator, heat transfer to the liquid refrigerant is utilized for operation of the sensor system rather than heat transfer to the superheat, resulting in a far more stable and efficient refrigeration control.

Abstract: A hydraulic piston machine is disclosed, having a piston arranged to move back and forth in a cylinder body. In such a machine it is desirable to be able to achieve a longer service life, even when the hydraulic medium is not suitable for lubricating the bearing faces. For that purpose, at least on its outer face sliding on the cylinder body, the piston has a layer of a friction-reducing plastics material, wherein at the end of the piston there is provided a bearing face of an articulated joint by means of which a slide shoe is connected, articulated to the piston, the layer being continued onto the bearing face.

Abstract: A two-way seat-type valve is provided, having a valve seat which is arranged between a first and a second connection, and having a closure element which co-operates with the valve seat, is arranged in a guide so as to be movable towards the valve seat or away from the valve seat, and which is subjected to a control pressure prevailing in a pressure chamber on the side, remote from the valve seat, of the closure element. A valve of this type should also be able to exhibit good reaction characteristics with water as hydraulic fluid. For this purpose, the closure element is guided seallessly in the guide.

Abstract: A process for controlling a refrigeration system, as well as the refrigeration system and a new expansion valve for the refrigeration system. An electronic regulator is used to operate a sensor system having a device for applying heat power to the sensor system in direct dependence on sensed superheat of the refrigerant leaving the evaporator. By locating the sensing system in communication with liquid refrigerant upstream of the evaporator, heat transfer to the liquid refrigerant is utilized for operation of the sensor system rather than heat transfer to the superheat, resulting in a far more stable and efficient refrigeration control.

Abstract: There is disclosed a method and system for improving the user interface between operator and motor controller, in particular a frequency converter. According to the invention, instead of presenting all information on a display at one time, a method of programming the motor controller is suggested, in which the operator is guided through the set up procedure, so that only relevant parameters are displayed on the different views. Another aspect of the invention is a method of programming a motor controller not in terms of parameter and parameter numbers, but in physical, technical and process terms. In this way, a high level mode of programming a motor controller is achieved, because the user interface does not deal with the less interesting motor controller specific parameters, but instead allows the operator to program the unit in terms he uses.

Abstract: A hydraulic control system for work vehicles including a control unit to control the steering wheels of a vehicle via a cylinder and a priority valve which by a first load-sensing system controls the pressure fluid flow to the control unit and to a subsequent proportional valve group. By a second load-sensing system the proportional valve group controls the pressure fluid flow to secondary hydraulic motors or work cylinders to control the work tools of the vehicle. The control system also includes an open-centre valve connection and a fixed displacement pump. The first load-sensing system is connected with a second load-sensing system, whereby drop-off of the pressure fluid flow to the control unit is avoided at simultaneous operation of the latter and of one or several of the proportional valves as is the case with known control systems. Hereby a control system is provided which is particularly agreeable to operate for the driver of the work vehicle.