The invention relates to a method for cont- rolling a pressure fluid operated apparatus, defined in the introductory section of patent claim 1.

The invention also relates to an arrangement for controlling a pressure fluid operated apparatus, defined in the introductory section of patent claim 4. In the prior art there is known a control arrangement for a hydraulic cylinder, where by using slide valves and on/off regulation, pressure oil is conducted to either side of the piston of a hydraulic cylinder, and the piston and its shaft are shifted to a desired distance.

A drawback with the above mentioned arrange¬ ment is that the piston shaft cannot be moved accurate¬ ly, and that there is therefore needed separate locati¬ on sensors for defining the exact location of the pis- ton shaft. Moreover, the piston does not remain exactly in place, but tends to slide owing to the effect of the pressure, and corrective control operations are requi¬ red in order to maintain the position of the piston. Another drawback of this arrangement is that the ini- tial and final accelerations are not under control.

The object of the invention is to eliminate the above mentioned drawbacks. A particular object of the invention is to provide an improved method for controlling pressure fluid operated apparatuses with precision.

The method of the invention is characterized by what is stated in the patent claim 1.

In the method of the invention for controlling a pressure fluid operated apparatus by means of a cont- rol unit and a valve system, when the control unit is in operation, the control members are moved and their motion affects the valve devices of the valve system.

so that the pressure fluid flows to the apparatus and its pressure urges the apparatus, moving its outlet; and that the motion of the apparatus outlet or a compa¬ rable motion is coupled back to the control unit, so that the reactive motion eliminates the motion of the control members of the said control unit, and as a consequence the motion of the control members is essen¬ tially stopped, in which case they still affect the valve devices of the valve system, so that the pressure fluid flows, during the operation of the control unit, to the apparatus, and the fluid pressure urges the apparatus; and that the stopping of the control unit causes the back-coupled motion of the apparatus to shift the control members, and their control over the valve devices of the valve system ends, which results in the stopping of the apparatus.

In a preferred application of the method, the pressure fluid is arranged to flow, during the operati¬ on of the control unit, in a controlled fashion out of the apparatus through the valve devices of the valve system, so that the outlet end of the apparatus also is subjected to pressure, but to a lower pressure than the inlet end.

In another preferred application of the met- hod, the said back-coupling is realized by suitably changing the rotary motion of the apparatus outlet or the like to linear motion, which is transmitted to the control unit.

In another preferred application of the met- hod, the back-coupling is realized mechanically.

The arrangement of the invention is characte¬ rized by what is stated in the patent claim 4.

The arrangement of the invention for control¬ ling a pressure fluid operated apparatus comprises a control unit and a valve system. According to the in¬ vention, the control unit includes a motor element, such as an electric motor, advantageously a stepping

motor, and control members provided in connection the¬ reto, which control members are moved by means of the motor element; the valve system includes two valve devices, which are manipulated by moving the control members of the control unit; the first valve device is manipulated by shifting the control members to one direction, and the second valve device is manipulated by shifting the control members to another direction; while manipulating the first valve device, pressure fluid is conducted to the apparatus in order to run it in one direction, and respectively while manipulating the second valve device, pressure fluid is conducted to the apparatus in order to run it in the opposite direc¬ tion; and the arrangement comprises means for coupling the motion of the apparatus back to the control unit, so that the motion of the control members, generated by the motor element, is eliminated by a reactive motion when the motor element is used, after which the motion of the control members is essentially stopped, but the control members still control the valve devices of the valve system, so that during the operation of the motor element, pressure fluid flows to the apparatus and the pressure urges the apparatus, and that the stopping of the motor element makes the control members to shift, and ceases their control over one or the other of the valve devices, in which case the apparatus stops.

In a preferred embodiment of the arrangement, each of the two valve devices includes a first valve which is arranged in between the apparatus and the pressure fluid tank in order to regulate the outlet flow of the fluid.

In another preferred embodiment of the arran¬ gement, each of the two valve devices comprises, in addition to the first valve, also a second and a third valve, which all are co-operated, and among which val¬ ves: the second valve is arranged in between the pres¬ sure fluid tank and the third valve in order to control

the third valve, and this second valve is manipulated by shifting the control members of the control unit; the third valve is arranged in between the pressure fluid pump or a corresponding supply and the apparatus in order to regulate the supply flow of the pressure fluid.

In another preferred embodiment of the arran¬ gement, each of the two valve devices includes a fourth valve which is arranged in connection with the third valve, in between the pressure fluid pump or a corres¬ ponding supply and the first and second valves, and by means of this fourth valve, the first and third valves are closed after the control power of the control mem¬ bers over the second.valve has ended. In another preferred embodiment of the arran¬ gement, the control members of the control unit comp¬ rises a control axis and a lever device, which is moved by means of the control axis.

In another preferred embodiment of the arran- ge ent, the means for coupling the motion of the appa¬ ratus back to the control unit comprise a device for turning rotary motion into linear motion, and by means of this device, the rotary motion of the apparatus is changed into linear motion and transmitted to the cont- rol unit, advantageously to the control axis thereof. In another preferred embodiment of the arran¬ gement, in connection with the control unit there is provided a device for turning rotary motion into linear motion, by means of which device the rotary motion of the motor element is changed into linear motion of the control axis.

In another preferred embodiment of the arran¬ gement, the device for turning rotary motion into li¬ near motion, provided in connection with the control unit, and the back-coupling devices for the motion of the apparatus for turning rotary motion into linear motion, are combined into one single device.

In another preferred embodiment of the arran¬ gement, the device for turning rotary motion into li¬ near motion is a ball-nut arrangement.

In another preferred embodiment of the arran- gement, the apparatus is a pressure fluid cylinder, comprising in conventional fashion a piston, a piston shaft and a cylindrical chamber; in connection with the said piston, there are provided means for changing the linear motion of the piston into rotary motion, the said means being for example a turning nut or screw.

In another preferred embodiment of the arran¬ gement, the apparatus is a swing device comprising a cylindrical chamber, a turning axis fitted in the cy¬ lindrical chamber, and conduits for feeding the pressu- re fluid into the cylindrical chamber and for dischar¬ ging it therefrom; the turning axis is provided with a blade-like stop, extending from the turning axis to the inner wall of the cylindrical chamber, and the cylin¬ drical chamber includes a partition wall extending from the inner wall of the cylindrical chamber to the tur¬ ning axis; and the said stop, turning axis and partiti¬ on wall divide the cylindrical chamber into two sub- chambers, and conduits are connected to both of these sub-chambers. The turning axis has two extreme posi- tions, between which the turning angle of the turning axis can be adjusted by conducting pressure fluid into the sub-chambers and out of them via the conduits. The swing device can also be realized as a hydraulic motor or other such rotary pressure fluid operated apparatus. In that case the adjusted angle is a desired section of 360° + n x 360°, where n = integral.

In another preferred embodiment of the arran¬ gement, the first and second valves of each valve devi¬ ce are arranged in connection with a intermediate space or the like, which space is connected to the tank; and the third valves are arranged in connection with a second intermediate space or the like, which space is

connected to the pump or other corresponding pressure fluid source.

In another preferred embodiment of the arran¬ gement, the first valves of the valve devices are pro- vided with a casing, advantageously surrounding a cy¬ lindrical chamber; a spindle which is axially movable in the lengthwise direction of the chamber; a socket; and a first aperture, the said socket and aperture being located in the first end of the chamber, and the first intermediate space and the chamber being inter¬ connected through this first aperture; and a second, advantageously annular aperture provided in the casing, through which aperture the apparatus is respectively connected to the chambers of the first valves; by mo- ving the spindles, the flow path and the discharge flow of the pressure fluid froπuthe apparatus to the tank can be regulated.

In another preferred embodiment of the arran¬ gement, the third valves of the valve devices advanta- geously comprise a cylindrical casing with a chamber inside; a spindle, which is axially movable in the lengthwise direction of the chamber; a socket; and a first aperture, the said socket and aperture being located in the first end of the chamber, and through this aperture, the second intermediate space and the chamber are interconnected; and a second advantageously annular aperture, which is provided in the casing and through which aperture the apparatus is respectively connected to the chambers of the third valves; by mo- ving the said spindles, the flow path and the supply flow of the pressure fluid from the pump or correspon¬ ding source to the apparatus can be regulated.

In another preferred embodiment of the arran¬ gement, the second valve includes a spring-loaded val- ve, the closing member whereof is manipulated, against the spring load, by the control members of the control unit, in order to open the flow path from the rear

chamber of either of the third valves through the con¬ duit further to the first intermediate space and the tank, so that the spindle of either of the third valves is shifted and opens the flow path for the pressure fluid from the second intermediate space to the appara¬ tus.

In another preferred embodiment of the arran¬ gement, each second valve is respectively arranged in the spindle of the first valve; i.e. the control mem- bers can manipulate the spindle of the second valve, so that through the second valve, a flow path can be opened from the first intermediate space to the rear chamber of the first valve, which rear chamber is furt¬ her connected, by means of a conduit, to the rear cham- ber of the third valve.

In another preferred embodiment of the arran¬ gement, each fourth valve is a back-pressure valve, which most advantageously is arranged in the spindle of each third valve, so that the pressure fluid from the pump or other such source is discharged therethrough to the rear chamber of the third valve, and further via the conduit to the rear chamber of the first valve.

An advantage of the invention is that it brings forth a simple, accurate and reliable control arrangement for a pressure fluid operated apparatus.

^• Another advantage of the invention is that it realizes a pressure fluid operated, advantageously hydraulic, control arrangement with a closed pressure fluid system. This closed system is pressure-proof and compact in construction.

Another advantage of the invention is that the said closed pressure fluid system also is a so-called rigid system, where pressurized conditions prevail, practically always, in the apparatus in between the inlet and outlet, for instance on both sides of the piston or a corresponding member. As a result of the closed pressure fluid system and the rigid pressure

conditions, the control system in general is accurately controllable and does not vibrate easily. Moreover, the velocities of the apparatus in moving the piston or the like member can rise remarkably high. Yet another advantage of the invention is that through the control unit, the apparatus can be control¬ led directly, preferably electrically. The position of the outlet of the apparatus is always known exactly, when the starting position is known. There is no need for separate measuring devices in connection with the apparatus in order to define locations.

Yet another advantage of the invention is that the control method and arrangement can easily be ap¬ plied, without changes, to pressure fluid operated apparatuses of various sizes, for example to hydraulic cylinders and hydraulic motors. The control pressure fluid circuit is an auxiliary circuit, separate from the operating pressure fluid circuit proper, wherefore control pressures are relatively low and independent of the operating pressure.

In the following the invention is explained in more detail with reference to the appended drawings, where figure 1 illustrates a longitudinal cross-section of an arrangement of the invention for controlling a pressure fluid operated apparatus; figure 2 illustrates a longitudinal cross-section of valves belonging to the valve system of the arrangement of the invention; figu¬ re 3 illustrates the cross-section A-A of the arrange¬ ment of figure 2; figure 4 illustrates a longitudinal cross-section of an arrangement of the invention for controlling a pressure fluid operated cylinder; figure 5 illustrates an arrangement of the invention for cont¬ rolling a pressure fluid operated swing device; and figure 6 illustrates the cross-section K-K of the swing device of figure 5.

The arrangement of the invention for control¬ ling a pressure fluid operated apparatus comprises a

control unit 1, a valve system 7 and means 6 for coup¬ ling the motion of the apparatus back to the control unit 1.

In figure 1, the control unit 1 comprises a motor element 2, advantageously a stepping motor, and control members provided in connection thereto, i.e. a control axis 3 and lever device 5. The stepping motor 2 is connected to the control axis 3, which is rotated by the stepping motor. The control axis 3 is supported, by means of a sleeve bearing 4, to the housing 12. The sleeve bearing 4 also allows axial motion for the cont¬ rol axis 3. The insertion of the first end of the cont¬ rol axis 3 through the aperture 13a to outside the housing 12 is provided with a sealing 14. In this end of the axis, there is in turn connected the stepping motor 2, which is provided in a suitable protective space 15. The second end of the control axis 3 is brought, via the aperture 13b, to the coupling member 47. In connection with the control unit 1, there is provided a device for turning rotary motion into linear motion. In this case in the second end of the control axis 3, there is connected a ball-nut arrange¬ ment 16. The rotary motion F, G transmitted to the control axis 3 of the stepping motor 2 by means of this device, is changed into linear lengthwise motion of the control axis, and the direction B, C of this motion in figure 1 is dependent on the rotary motion F, G of the stepping motor 2 and the control axis 3. The lever device 5 of the control members is attached to the control axis 3, so that the control axis is free to rotate in the aperture 5a of the lever device 5. By means of brackets 5b or the like of the control axis, the control axis 5 is, however, connected to the axis 3, so that it moves together with the axis while this axis is moved in linear direction. The lever device 5 protrudes out of the axis 3, advantageously on

a plane at right angles with respect to the axis. In the free end of the lever device 5, there are arranged brackets 17a, 17b and pins 18a, 18b. The brackets 17a, 17b are advantageously formed of opposite ends of a preferably uniform, straight bar. In this case this bar is essentially parallel to the axis Al-Al of the cont¬ rol axis 3.

The valve system 7 comprises two valve devices 7a and 7b, which are arranged in connection with each other and advantageously cross-coupled as a co-opera¬ ting unit. Both valve devices are advantageously simi¬ lar and they are installed inside the housing 12. The two valve devices have a common inlet conduit 19 for the pressure fluid, and this inlet conduit is connected to the pump P or to a corresponding pressure fluid source. Respectively, the valve devices have a common outlet conduit 20 for the pressure fluid, and this outlet conduit is connected to the tank T for dischar¬ ging the pressure fluid from the valve system 7. The tank T is connected, by means of a conduit, to the suction side of the pump P. From the tank T, pressure fluid is pumped, by means of the pump P, back to the valve system while the arrangement is switched on. Moreover, both valve devices are provided with a con- ducting channel 21a, 21b to ^" the pressure fluid operated apparatus 22.

The two valve devices 7a, 7b of the valve system 7 are manipulated by shifting the control mem¬ bers of the control unit 1, i.e. the control axis 3 and lever device 5, by means of the motor element 2. This is carried out so that the first valve device 7a is manipulated by shifting the control members in the first direction B, and the second valve device 7b is manipulated by shifting the control members in another, i.e. opposite direction C. When manipulating the first valve device 7a, pressure fluid is conducted from the pump P to the inlet conduit 19, and through the first

valve device to the channel 21a and further to the apparatus 22 in order to run the apparatus in one di¬ rection. Pressure fluid is discharged from the appara¬ tus 22 via the second connecting channel 21b and second valve device 7b further to the outlet conduit 20 and tank T. Respectively, when manipulating the second valve device 7b, pressure fluid is conducted to the apparatus via the inlet conduit 19, the second valve device 7b and the channel 21b, and it is discharged from the apparatus 22 through the first connecting channel 21a, the first valve device 7a and the outlet conduit 20, further to the tank T.

In the embodiment of the appended drawings, each of the two valve devices 7a, 7b advantageously includes four valves. The first valve 8a; 8b is arran¬ ged in between the apparatus 22 and the tank T in order to regulate the discharge flow of the pressure fluid. The second valve 9a; 9b is located in between the tank T and the third valve 10a; 10b in order to control the third valve. The third valve 10a; 10b is arranged in between the pump P or corresponding source and the apparatus 22 in order to regulate the supply flow of the pressure fluid. The fourth valve 11a; lib is ar¬ ranged in connection with the third valve 10a; 10b, in between the pump P or corresponding source, and the first and second valves, by means of which fourth valve the first 8a; 8b and the third 10a; 10b valves are closed after the control over the second valve 9a; 9b has ended. The arrangement of the invention comprises means for coupling the rotary o_' linear motion of the apparatus 22 back to the control unit 1, in this case to the control axis 3. In the embodiment of figure 1, the motion generated with the pressure fluid operated apparatus 22 in its outlet 22a is rotary motion D, E. In that case the said means comprise a device for chan¬ ging rotary motion into linear motion, by means of

which device the rotary motion of the outlet 22a or the like of the apparatus 22 is changed into linear motion and transmitted to the control axis 3 of the control unit 1. In this case the device for turning rotary motion into linear motion is a ball-nut arrangement 16. Thus the device for changing rotary motion into linear motion provided in connection with the control unit, and the back-coupling devices of the motion of the apparatus 22 for turning rotary motion into linear motion are combined in one single device, i.e. the ball-nut arrangement 16.

By means of the back-coupling equipment, i.e. the ball-nut arrangement 16, the rotary motion D, E of the apparatus 22 is coupled onto the control axis 3 of the control unit 1 and changed to linear motion of the axis, either in the direction B or C. The stepping motor 2 has generated the rotary motion F, G of the control axis, which by means of the ball-nut arrange¬ ment 16 also is changed into linear motion of the cont- rol axis 3, either in the direction B or C. These said linear motions of the control axis 3 take place in opposite directions and are equal in range, i.e. they are eliminated when the stepping motor 2 is in use. The stopping of the stepping motor 2 does not immediately interrupt the apparatus 22, but the apparatus continues running for a while and causes a reactionary motion to the control axis 3. As a consequence, the control ef¬ fect of the control members, i.e. the control axis 3 and the lever device 5, over either one of the valve devices 7a, 7b of the valve system 7 is ceased, which brings the apparatus 22 to a stop.

The structure of the valve system 7 applied in the embodiments of the drawings is explained in more detail with reference to figure 2. The valve devices 7a, 7b of the valve system 7 are interconnected as a co-operative unit. The first 8a, 8b and second 9a, 9b valves are arranged in connec-

tion with a first intermediate space 23 or the like. This intermediate space 23 is connected, via the outlet conduit 20, to the tank T. The third valves 10a, 10b are arranged in connection with a second intermediate space 24 or the like. This intermediate space 24 is connected, via the inlet conduit 19, to the pump P or a corresponding pressure fluid source. The fourth valves 11a, lib are also arranged in connection with the se¬ cond intermediate space 24 or the like. The first valve 8a, 8b comprises a casing 25a,

25b, inside which there is advantageously provided a cylindrical chamber 26a, 26b; a spindle 27a, 27b, which is axially shiftable in the lengthwise direction of the chamber; a socket 28a, 28b; a first aperture 29a, 29b, which socket and aperture are located at the first end of the chamber, and through which aperture the first intermediate space 23 and the chamber 26a, 26b are connected to each other; and another, advantageously annular aperture 30a, 30b, which is arranged in the casing 25a, 25b, and opens into the chamber 26a, 26b. In the other end of the first valve 8a, 8b, there is provided a rear space 31a, 31b. In this space, there is also arranged a spring member 32a, 32b in between the spindle 27a, 27b and the chamber bottom. The second apertures 30a, 30b of the first valves 8a, 8b are connected to respective channels 21a and 21b, and further therethrough to the pressure fluid operated apparatus 22. By suitably shifting each spin¬ dle 27a, 27b, the flow path in between the first aper- ture 29a, 29b, and the second annular aperture 30a, 30b can be regulated, as well as the pressure fluid di¬ scharge flow from the apparatus 22 to the tank T.

The third valve 10a, 10b includes correspon¬ ding members as the first valve 8a, 8b, and they are advantageously similar. Thus the third valve 10a, 10b comprises a casing 33a, 33b, inside which is provided a cylindrical chamber 34a, 34b; a spindle 35, 35b, which

is axially movable in the lengthwise direction of the chamber; a socket 36a, 36b; a first aperture 37a, 37b, which socket and aperture are located in the first end of the chamber, and through which apeerture the second intermediate space 24 and the chamber 34a, 34b are interconnected; another, advantageously annular apertu¬ re 38a, 38b, is provided in the casing 33a, 33b, and the said aperture opens into the chamber 34a, 34b. In the other end of the chamber of the third valve 10a, 10b, there is provided the rear space 39a, 39b. In this space, there is also arranged a spring member 40a, 40b in between the spindle 35a, 35b and the chamber bottom. The second apertures 38a and 38b of the third valves 10a, 10b are respectively connected to the channels 21a and 21b, which connect both valve devices to the appa¬ ratus 22. By suitably shifting each spindle 35a, 35b, the flow path in between the first aperture 37a, 37b and the second aperture 38a, 38b can be regulated, as well as the inlet flow of the pressure fluid from the pump P or a corresponding source to the apparatus 22. The second valve 9a, 9b is arranged in con¬ nection with the first valve 8a, 8b of the valve device 7a, 7b, so that by means of them, the first interme¬ diate space 23 can be connected to the rear chamber 31a, 31b of the first valve 8a, 8b via a channel 41a, 41b. In the embodiments of the drawings, the second valve 9a, 9b is arranged in the spindle 27a, 27b of the first valve, so that it moves along with the spindle. Thus the position of the first valve 9a, 9b, as well as its distance from the brackets 17a, 17b and pins 18a, 18b of the control members also have a regulating in¬ fluence on the first valve 8a, 8b and to the flow path of the discharging pressure fluid. By means of this arrangement, the first 8a, 8b and second 9a, 9b valve can be installed in connection to each other, so that the discharge flow from the apparatus is controlled, and that the pressure in the apparatus, on the outlet

conduit side, is suitable and somewhat lower than the operating pressure.

The second valve 9a, 9b includes a locking member 42a, 42b arranged in the channel 41a, 41b, which locking member is charged with a spring member 43a, 43b. Normally the locking members 42a, 42b of the se¬ cond valve 9a, 9b close the channel 41a, 41b. The cont¬ rol members of the control unit 1, i.e. the control axis and the pins 18a, 18b of the lever device 5 are used for urging the spring load of the locking members 42a, 42b, in order to open the channel 41a, 41b.

The first and second valve devices 7a, 7b are cross-coupled, so that the rear chamber 31a of the first valve 8a of the first valve device 7a is connec- ted, by a channel 44, to the rear space 39b of the third valve 10b of the second valve device 7b. Respec¬ tively, the rear chamber 31b of the first valve 8b of the second valve device 7b is connected, by a channel 45, to the rear chamber 39a of the third valve 10a of the first valve device 7a.

The fourth valve 11a, lib is a back-pressure valve, which is most advantageously arranged in the spindle 35a, 35b of the third valve 10a, 10b, so that pressure fluid from the pump P or other source is fed, through this valve and via the second intermediate space 24 to the rear chamber 39a, 39b of the third valve. From the rear chambers 39a, 39b of the third valves, the pressurized fluid is conducted, via the channels 44, 45, crosswise to the rear chambers 31b and 31a of the first valves of the valve devices 7b, 7a, and further, via the second valve 9b, 9a - if this channel 41b, 41a is open - to the second intermediate space 24 and further to the tank T.

The cross-sectional area of the flowthrough channel of the first valve 11a, lib is essentially smaller than the apertures 37a, 37b and 38a, 38b of the third valve 10a, 10b, through which apertures the pres-

sure fluid flows to the apparatus 22. Only a relatively small control flow passes through the fourth valve into the rear chambers 39a, 39b and 31a, 31b of the third 10a, 10b and first 8a, 8b valves respectively. The cross-sectional areas of the spindles 27a,

27b and 35a, 35b of the first 8a, 8b and third 10a, 10b valves of both valve devices 7a, 7b are at the first end of the spindle, i.e. at the aperture 29a, 29b, and 37a, 37b respectively, smaller than the cross-sectional areas of the other end of the spindle on the side of the rear chambers 31a, 31b and 39a, 39b respectively. By means of this arrangement, both the first and third valve are closed always when equally high pressures prevail on both sides of the valve spindles. Thus the said valves are, as a rule, always operated by the pressures that affect them. The purpose of the spring members 32a, 32b and respectively 40a, 40b, located in the rear chambers 31a, 31b and 39a, 39b of the valves respectively, is mainly to ensure that when pressures drop for one reason or another, these valves are always closed and prevent the pressure fluid from being di¬ scharged from the apparatus 22. Thus the outlet of the apparatus 22 remains locked in place.

According to the embodiments illustrated in the drawings, the valve system 7 is provided inside the casing 12. The first vaves 8a, 8b of each valve device 7a, 7b of the valve system 7 are advantageously arran¬ ged so that the lengthwise axes of these chambers 26a, 26b are located on one straight line, and that the brackets 17a, 17b and pins 18a, 18b of the lever device 5 of the control unit 1 are placed in the second inter¬ mediate space 24, in between the spindles 27a, 27b and the second valves 9a, 9b, more specifically in between their locking members 42a, 42b and the channels 41a, 41b.

The third valves 10a, 10b of both valve devi¬ ces 7a, 7b are arranged in similar fashion as the first

valves 8a, 8b, so that the lengthwise axes of the cham¬ bers 35a, 35b are located on one straight line.

In the embodiments illustrated in the dra¬ wings, in between the first valves 8a, 8b and third valves 10a, 10b of the valve devices 7a, 7b, there is provided an intermediate housing 46. The channels 21a, 21b from the valve devices 7a, 7b to the apparatus 22 are connected to the bores of the intermediate housing 46, and further therethrough to the aperture 30a of the first valve 8a and to the aperture 38a of the third valve 10a of the valve device 7a respectively, and to the aperture 30b of the first valve 8b and the aperture 38b of the third valve 10b of the valve device 7b res¬ pectively. In between the apparatus 22 and the control axis 3 of the control unit^l, there are provided means for changing rotary motion into linear motion, advanta¬ geously a ball-nut arrangement 16. This is fitted in the space 48 of the coupling member 47. The ball-nut arrangement 16 includes a sleevelike member 49, which is attached to the control axis 3, parallelly to this axis Al - Al; and a nut member 50, which is connected to a rotary transmitting member 51. The nut member 50 is provided with a groove 52, which is advantageously threaded, with an angle α of thread. In the sleevelike member 49, there is installed a ball 53, which follows the groove 52 of the nut member 50, so that while rota¬ ting the nut member 50, the sleevelike member 49 is shifted axially, and simultaneously shifts the control axis 3 to the direction B or C, depending on the direc¬ tion of rotation of the nut member.

The transmitting member 51 is coupled with bearings to the coupling member 47, so that its linear motion is prevented. This transmitting member 51 is connected to the outlet of the apparatus 22, such as to a rotary axis or the like.

Figure 3 illustrates a preferred embodiment of

the invention, where the apparatus is a pressure fluid cylinder 54. This pressure fluid cylinder 54 comprises, in known fashion, a piston 55, a piston shaft 56 and a cylindrical space 57. In connection with the piston 55, there are arranged means for changing the piston's linear motion into rotary motion. In this case the said means provided in connection with the piston include a turning nut 58 and screw 59. The piston 55 is connected to the turning nut 58 and the nut further to the tur- ning screw 59. The screw 59 is connected to the trans¬ mitting member 51 of the coupling member 47, and furt¬ her to the ball-nut arrangement 16 or the like. When moving the piston 55 in the direction B', C parallel to the cylinder axis, the piston 55 and the turning nut 58 are supported against the casing 60 of the cylinder 54 in order to prevent them from rotating. Thus their linear motion is transmitted, by means of the threa- dings between the turning nut 58 and screw 59 to rotary motion of the screw 59, and further via the transmit- ting member 51 to the ball-nut arrangement 16.

The operation of the arrangement of the in¬ vention is explained below with reference to figures 1 and 3.

Let us suppose that the pump P is in operation and that pressure fluid is pumped to the second inter¬ mediate space 24 of the valve system 7. From the second intermediate space 24, the pressurized fluid is di¬ scharged, via each fourth valve 11a, lib, respectively to the rear chambers 39a, 39b of the third valves 10a, 10b, and further, via the channels 44, 45, to the rear chambers 31a, 31b of the first valves 8a, 8b. The first 8a, 8b and third 10a, 10b valves are now closed by means of the pressurized fluid (secured by the spring members 32a, 32b and 40a, 40b) . A command to start operation is given to the stepping motor 2, and according to the command, the connected control axis 3 is started to rotate clockwise

in the direction F. Owing to the influence of the ball- nut arrangement 16, the control axis 3, as well as the connected stepping motor 2 in this example, are shifted in the direction B. The length of the shifting distance to the direction B is such that the pin 18a of the bracket 17a belonging to the control unit 1 opens the second valve 9a, so that the channel 41a, in between the first intermediate space 23 and the rear space 31a of the first valve, is opened. Along with the opening of the second valve 9a, the fluid pressure in the rear chamber 31a of the first valve 8a of the first valve device 7a, and in the rear chamber 39b of the third valve 10b of the second valve device 7b drops, after which the spindle 35b of the said third valve 10b is shifted, urged by the pressure directed towards it from the intermediate space 24, and the flow path is opened from the pump P via the second intermediate space 24a, the aperture 37b and further to the channel 38b, channel 21b and to the apparatus 22. Thus the pressure of the pump P begins to affect the apparatus 22.

In figure 3, the apparatus 22 is a pressure fluid cylinder, advantageously a hydraulic cylinder 54, and in this embodiment the pressure of the pump P be- gins to urge the piston 55 of the cylinder, so that the piston 55 is shifted in the direction B*. By interme¬ diation of the turning nut 58, the linear motion of the piston 55 is changed into rotary motion D of the tur¬ ning screw 59. This rotary motion is transmitted, by the transmitting member 51, to the ball-nut arrangement 16. The ball-nut arrangement 16 in turn changes the rotary motion D into linear motion, so that the control axis 3 is shifted in the direction C, i.e. in the di¬ rection which is opposite to the linear motion in the direction B, generated by means of the stepping motor 2. These motions in the directions B and C compensate each other, so that the lever device 5 of the control

unit 1 remains essentially in place and tends to keep the second valve 9a continuously open.

At the same time, pressure fluid is dischar¬ ged, through the second channel 21a, out of the appa- ratus 22. The fluid is conducted from the channel 21a through the aperture 30a to the first valve 8a of the first valve device 7a. The pressure of the draining pressure fluid affects the spindle 27a of the first valve and urges it towards the rear chamber 31a, in which case the first aperture 29a opens, and the pres¬ sure fluid is discharged into the first intermediate space 23 and further to the tank T via the outlet con¬ duit 20. The pressure of the draining pressure fluid defines how much the spindle 27a of the first valve 8a moves and how much it opens the first aperture 29a. Thus the pressure fluid is discharged in a controlled fashion from the apparatus 22.

The discharge of the draining pressure fluid through the first valve 8a is also regulated by means of the second valve 9a. When the spindle 27a of the first valve 8a is shifted in the chamber 26a towards the rear chamber 31a, the second valve 9a is shifted along with the spindle 27a. The lever device 5 of the control unit 1, and particularly the pin 18a, keeps the second valve 9a open for a given permitted shifting length of the spindle 27a. If this length is surpassed, the influence of the pin 18a to the closing member 42 of the second valve 9a is interrupted, and the valve 9a is closed; pressure fluid is again conducted through the fourth valve lib of the second valve device 7b and through the channel 44 of the rear chamber 39b of the third valve 10b to the rear chamber 31a of the said first valve 8a, and affects the spindle 27a by urging it towards the socket 28a by restricting the aperture 29a. At the same time, the other valve 7a is returned under the control of the control unit 1, and the situ¬ ation is normalized.

In the above described fashion, pressure fluid is discharged, in the embodiment of figure 3 alike, on the other side of the piston 55 of the cylinder 54, via the channel 21a and the first valve 8a of the first valve device.

When the apparatus 22 should be stopped, the procedure is as follows. The stepping motor 22 is swit¬ ched off, so that the rotary motion F of the control axis 3 and its axial motion in the direction B are stopped. However, the fluid pressure still affects in the apparatus 22 through the third valve 10b of the second valve device 7b. Thus the motion of the appa¬ ratus 22 affects, via the transmitting member 51, the ball-nut arrangement 16, whereby the control axis is shifted in the direction C. This means that the control axis 3, the lever device 5, the connected bracket 17a and pin 18a cease to press the locking member 42a of the second valve. The second valve 9a is closed, and pressurized fluid is discharged through the fourth valve lib of the second valve device to the rear cham¬ ber 39b of the third valve 10b, and further, through the channel 44, to the rear chamber 31a of the first valve 8a of the first valve device 7a. Owing to this pressure, the first valve 8a is closed. In respective fashion, the third valve 10ij of the second valve device 7b is closed, in which case the pressure fluid flow from the pump P and via the channel 21b of the third valve 10b of the intermediate space 24 further to the apparatus 22 is stopped. At the same time, the motion D of the outlet 22a of the apparatus 22 ceases, and furt¬ her, due to the influence of the back-coupling means, i.e. the ball-nut arrangement 16, the linear motion C of the control axis 3 of the control unit 1, as well as the lever device 5 plus connected equipment, are stop- ped.

When the direction of operation of the outlet 22a of the apparatus 22 is wished to be changed with

respect to the above, i.e. from the direction D to the direction E, or respectively in figure 4 from the di¬ rection B of the piston 55 to the direction C thereof, the stepping motor 2 is made to run counterclockwise, in which case the control axis 3 is shifted, owing to the influence of the ball-nut arrangement 16, in the direction C, i.e. in an opposite direction as compared to the above specification. Now the control axis 3 of the control unit 1 and the means 17a, 18a connected to the lever device 5 are used for manipulating the second valve 9b of the second valve device 7b in similar fashion as was described above, with reference to the first valve device 7a. The operation of the second valve device 7b is completely analogous to the above described operation of the valve device 7a. Only the pressure fluid flows, passing through the channels 21a, 21b, proceed in an opposite direction, which means that the running direction of the apparatus 22 is changed. In similar fashion, the motion of the apparatus 22 is coupled through the back-coupling means 6 to the motion of the control axis 3 with respect to the opposite di¬ rection.

Figure 5 illustrates a preferred embodiment of the arrangement of the invention, where the apparatus is a pressure fluid operated swing device 61. The swing device 61 comprises, as is seen in the crosssectional drawing 6, a pivoted axis 62, arranged in the cylinder space 63, in this case on its central axis. The cylin¬ der space 63 comprises the conduits 64 and 65, and through one of these, pressure fluid is conducted to the cylinder space, and through the other, pressure fluid is conducted out thereof. The cylinder space 63 also incorporates a partition wall 66 extending from the inner cylinder wall to the surface of the pivoted axis 62. The partition wall 66 is located in between the conduits 64, 65. The mutual installation of the pivoted axis 62 and the partition wall 66 is such that

the pivoted axis 62 has ample room to rotate, but so that pressure fluid is not essentially discharged in between the partition wall and the axis. In addition to this, the pivoted axis 62 is provided with a blade-like member 67 extending from the axis 62 to the inner wall of the cylinder space 63, and the mutual installation of the said blade 67 and the space 63 is such that pressure fluid is not essentially discharged in between the wall and the axis. Thus the partition wall 66, the pivoted axis 62 and the blade 67 divide the cylinder space 63 into two sections, the first 68 whereof is connected to the exterior of the swing device via the conduit 64, and the second section 69 is connected to the exterior via the second conduit 65. The pivoted axis 62 and its blade 67 have two extreme positions: the first extreme position H, and the second extreme position I, between which the pivoted axis 62 can be turned. The turning angle α between these extreme posi¬ tions is less than 360°, advantageously at least 300°. The conduits 64, 65 are connected to the channels 21a and 21b of the valve system 7 respectively. By conduc¬ ting pressure fluid via the conduit 64 to the first section 68, the pivoted axis 62 is turned around its central axis. Now the pressure fluid urges the blade 67 forward, so that the first section 68 grows and the second section 60 decreases. Pressure fluid is dischar¬ ged from the second section via the second conduit 65 and out of the swing device. Respectively, the swing device can be turned in the opposite direction by con- ducting pressure fluid to the second section 69 and by removing pressure fluid from the first section 68.

In principle the rotary motion of the pivoted axis 62 of the swing device 61 is coupled back to the control unit 1 in similar fashion as was explained above with reference to figure 1. The back-coupling is realized mechanically by means of a cogged belt 70 or corresponding mechanical transmitting gear. In the free

end of the pivoted axis 62 of the swing device, there is arranged a cogged surface 71 for the cogged belt, and respectively the back-coupling axis 72 of the coup¬ ling member 47 is provided with a cogged surface 73. In the coupling member 47, the backcoupling axis 72 is connected to the ball-nut arrangement 16 in similar fashion as was explained for example in connection with figure 1.

The operation of the swing device 61, and its controlling by means of the arrangement of the inven¬ tion, is in principle carried out in similar fashion as was explained above in connection with figure 4. With the swing device 61, the motion is rotary motion, and it is restricted, when defined in degrees, in between 0° - roughly 300°.

An advantage of the swing device 61 is that it is easily sealed, and an extremely accurate adjustment of the angle of turning is achieved thereby. Therefore it is suited for instance as an arm swinging device for a robot, or in other swing device applications re¬ quiring high precision. Another advantage of the in¬ vention is that an arrangement treating even large volumes of material can be realized on the basis the¬ reof. Instead of the above described swing device, the apparatus can be a hydraulic motor or a correspon¬ ding pressure fluid operated rotary device, the rota¬ tion whereof is in principle controlled in similar fashion as the operation of the swing device, for exam- pie. A hydraulic motor or the like can be controlled and adjusted with turning angles of α + n x 360 deg¬ rees, where n = integral.

It is pointed out that the motional distances of the control axis 3 in the direction of its axis Al-Al are relatively small, in the region of 5 mm or even less. Thus the control unit 1 and connected cont¬ rol members 2, 5 can quickly manipulate the respective

second valves 9a, 9b of the first or second valve devi¬ ce 7a, 7b of the valve system 7.

The motor element of the control unit 1, ad¬ vantageously a stepping motor, can be controlled from the control unit 1, comprising for instance a micro¬ processor. The motional momentum of the arrangement, for instance the length of the motion, or the degree or rate of revolutions, can be preset in the control devi¬ ce, and the performance can be supervised by counting the control pulses of the stepping motor. Many other programmable control methods, known in the prior art, are possible.

The invention is not limited to the above described embodiments only, but many modifications are possible within the scope of the inventional idea de¬ fined in the appended patent claims.