text: throughout all the figures , same or corresponding elements are generally indicated by same reference numerals . turning now to the drawing , and in particular to fig1 there is shown a drive according to the invention , used to drive a machine joint , comprised of a load mass 20 which is displaceable on the guides 18 , 19 in the direction x . the pump 3 is connected hydraulically to two chambers 16 , 17 of the cylinders 10 , 11 . the two cylinder rods 21 , 22 of the cylinders 10 , 11 are coupled mechanically via the load 20 . the arrangement thus acts in the same way as a single cylinder which is supplied in a closed hydraulic circuit with pressure oil from the pump 3 . the bearings 12 , 13 symbolize a fixed mechanical connection to the machine . the leakage line 4 of the pump 3 discharges a small oil stream into the tank 7 . the oil passes via the two non - return valves 5 , 6 back into the drive circuit again as soon as the pressure in one of the two pump connections falls below the pressure level in the tank 7 . the tank 7 may in this case be designed as a tank , a separate pump assembly or an other pressure source . when the arrangement moves in the direction x , the oil in the chamber 14 is displaced into the pressure accumulator 8 and consequently increases the pressure in the pressure accumulator 8 . the volume in the chamber 15 increases correspondingly and the pressure in the pressure accumulator 9 falls . this results in a restoring force which is defined by the pressures in the two chambers 14 , 15 and rises with an increasing deflection in the direction x . according to the invention , then , the components are designed in such a way that the restoring forces ideally assist the desired speed profile of the drive . if the pressures in the pressure accumulators 8 , 9 are selected very low or neglected , this results virtually in a straightforward close - circuit pump drive . with increasing pressure in the pressure accumulators , the spring forces of the pressure accumulators become higher and , in the case of an appropriate design , assist the desired cyclic movement of the load mass . the motor 2 , pump 3 , cylinder rods 21 , 22 and load mass 20 then no longer have to be accelerated solely by the electromagnetic forces of the motor 2 , but in this case are assisted by the pressure forces of the pressure accumulators . the nearer the desired movement comes to the natural oscillation of the system , the higher is the power share of the pressure accumulator forces and the lower is the power share of the motor . referring now to fig2 there is shown a particularly advantageous embodiment of a device according to the invention for driving a punching or embossing machine . the two cylinders 10 , 11 have been combined in a block 22 . two valves 24 , 25 have been introduced as an additional element . the cylinder chambers 14 , 15 can be switched to the tank 7 from the pressure accumulators 8 , 9 by means of the valve magnets 23 , 26 . consequently , the spring force is also switched away from the cylinders . when , during the cyclic movement of the shaft , the pressure accumulators are cut out after the reversal of movement , this results in a phase in the movement cycle which is driven only by the electric motor . this operating mode may be expedient when relatively large strokes are to be executed at an approximately constant speed . the cut - in and cut - out of the valves 24 , 25 can be controlled by the position of the piston rod , and the valves 24 , 25 may also be integrated in the cylinder . cut - in and cut - out then always take place at the same point . the drive thus behaves in the same way as a trampoline jumper who jumps on a spring and is thrown back by this in order thereby to execute an approximately force - free ballistic movement . according to the invention , the forces of the electric motor 2 are used only to influence the natural form of the movement , so that the resulting movement meets the requirements of the working process . the pressure accumulators 8 , 9 , 27 , 28 may also be used for further hydraulic secondary functions , such as , for example , small auxiliary pistons or valve pilot controls . there do not necessarily have to be four independent pressure accumulators , but the function of the oscillator may also be ensured by only one pressure accumulator . the punching tool consists of the parts , punching ram 20 , press plate 29 , die 30 , ejector 31 and the metal strip 32 to be machined . the tool indicated in this example of use is passive , that is to say the movement of the press plate 29 and ejector 21 is defined by hydraulic spring forces of the pressure accumulators 27 , 28 and mechanical movement limitation , without any specific movement control . further hydraulic functions with valve control may , of course , also be integrated in the tool . fig3 shows a further version of a device according to the invention . the machine joint is designed , here , as an injection unit 20 of an injection - moulding machine and has to apply very high forces and powers in the direction x , in order to press the plastic under high pressure into the die of a machine which is not depicted . after the injection operation , the injection unit has to be moved back into the initial position again under forces which are virtually disappearing . this asymmetric function is also reflected by an asymmetric design of the device according to the invention . if a relatively high pressure level in the accumulator 9 and a relatively large cross section of the cylinder chamber 15 are selected , the force range of the device is shifted towards positive forces in the direction x , along with correspondingly reduced forces in the opposite direction . in an extreme case , the accumulator 8 may be omitted . if the device has an appropriate design , the entire torque of the motor 2 is required in order to bring the piston rod 21 into the initial position prior to the injection operation or hold it in this position . during the subsequent injection operation , the motor 2 , pump 3 and pressure accumulator 9 work in the same direction . the powers of the pressure accumulator and the pump are thus added together . it can easily be seen that the power of the motor / pump assembly used can be doubled in this way . this can be converted into higher forces or a higher acceleration of the drive . this embodiment of a device according to the invention is therefore particularly suitable in machines which have to achieve very high forces or accelerations in only one direction . the valves 23 , 24 constitute a further special element of a device according to the invention . the valve magnets 25 , 26 switch the valves 23 , 24 and consequently connect the pressure accumulators 8 , 9 in each case to a delivery line of the pump . the pressurizing pressure in the pressure accumulators 8 , 9 can be varied in this way . the valves may in this case also be supplied by another independent pressure source . in addition to the pressurizing pressure , the neutral position may , of course , also be set by means of this device . we mean by neutral position the position of the piston rod 21 in which the pressure forces of the accumulators 8 , 9 are neutralized . fig4 shows a modified form of a device according to the invention for driving a toggle lever mechanism 20 . only a single cylinder 10 has been used . the pump 3 and pressure accumulators 8 , 9 have in this case no longer been connected in parallel , as in fig1 to 3 , but one behind the other ( in series ). accordingly , only two cylinder chambers 14 , 16 are required . however , the functioning of the device is not changed as a result . a hydraulic oscillator having the properties described in the preceding sections can also be implemented in this way . when the pump conveys oil from the cylinder chamber 16 into the pressure accumulator 8 , the pressure in the accumulator 8 rises and the piston rod 17 is displaced in the direction x , driven by the pressure forces in the chamber 14 . these pressure forces are thereby reduced . overall , the entire apparatus again acts in the same way as a spring / mass oscillator which can execute a cyclic movement ( natural oscillation ) even without external forces . a further special feature of the device according to the invention , shown in fig4 is the second pump assembly consisting of the motor 13 , pump 11 and pressure relief valve 15 . this unit generates a constant pressure on the non - return valves 5 , 6 and ensures that the pressure in the pressure accumulators 8 , 9 does not fall below a preset minimum value . the pump assembly also replaces leakage oil of the pump 3 which passes through the leakage - oil line 4 into the tank 7 . in fig5 the machine joint 20 is designed as a rotary joint . the device according to the invention corresponds in this case largely to the device in fig2 . however , the pressure accumulators 8 , 9 in fig2 have been replaced by a single pressure accumulator 8 which supplies both valves 24 , 25 with pressure oil . in addition , pressure sensors 28 , 29 , 33 , a position measuring system 34 and a control computer 31 have been depicted in fig5 . these elements were not depicted in fig1 to 4 for the sake of clarity , but make it possible to control the device more accurately . the position measuring system 34 may in this case also be integrated , in particular , in the cylinder or cylinders . in addition to the pressure and position , time derivations of these variables may also be recorded . the signals from the position measuring system 34 and pressure sensors 28 , 29 , 33 are available to the control computer 31 which activates the converter 1 according to a control algorithm , such as , for example , a state controller . the desired movement of the device xset 32 is in this case generated by an machine control master . this makes it possible to control the position and also the force which is exerted on the machine joint 20 by the device according to the invention . the control computer 31 may also be integrated in the converter or in the machine control master . in many applications , it is sufficient to record the pressure in only one cylinder chamber 14 , 15 , 16 , 17 . while the invention has been illustrated and described as embodied in a hydraulic oscillator as a drive of machines , it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit of the present invention . the embodiments were chosen and described in order to best explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated . what is claimed as new and desired to be protected by letters patent is set forth in the appended claims and their equivalents :