EP0859924A1

EP0859924A1 - Advanced valve arrangement

Info

Publication number: EP0859924A1
Application number: EP96938256A
Authority: EP
Inventors: Pentti Rita
Original assignee: Rita Leo
Current assignee: Rita Leo
Priority date: 1995-11-24
Filing date: 1996-11-22
Publication date: 1998-08-26
Also published as: FI955684A; WO1997020157A1; FI955684A0; FI103831B1; FI103831B

Abstract

The invention relates to an advanced valve arrangement (1) for controlling a pressure medium operated actuator. The valve arrangement (1) comprises two matched and cooperating valves (7, 8) and control members (45). According to the invention, the valve box (10) and stem (11) of the first valve (7) are divided, in the transfer direction of the stem (11), into two parts: the front space (12) of the valve box and the front part (28) of the stem, and the rear space (13) of the valve box and the rear part (29) of the stem. In the rear and front spaces (13, 12) of the valve box, there are arranged narrowing spots, where seats (310, 311) are fitted. The pressure medium channels (2, 14) and the actuator channels (5, 6) are arranged on different sides of the seats. In the rear and front part (28, 29) of the stem, there are arranged narrowing spots, provided with counterparts (312, 313) for the seats (310, 311), said counterparts and seats being pressed together in the closed position of the valve. In the rear and front part (29, 28) of the stem, there are provided connecting channels (17, 18), whereby the pressure medium channels (2, 14) and the actuator channels (5, 6) are inteconnected in the open position of the valve (7). The pump (P) is connected, by means of a control channel (19), to the rear space (13) of the first valve (7), so that the stem (11) of the first valve (7) is pressed into closed position by the pressure of the pressure medium. In said closed position, the connecting channels (17, 18) are closed, and at the same time the flowing of the pressure medium through the first valve (7) via both the feed and outflow channels (2, 3) is prevented. The second valve (8) is connected to a by-pass channel (23) provided in between the rear space (13) of the first valve (7) and the tank (T), and the control members (45) are arranged in connection with the second valve (8) in order to control the second valve (8) and therethrough the first valve (7) and the whole valve arrangement (1). The invention also relates to an advanced valve system utilizing this advanced valve arrangement.

Description

Advanced valve arrangement

The present invention relates to an advanced valve arrangement defined in the introductory part of claim 1 for controlling a pressure medium operated actuator.

The invention also relates to an advanced valve system defined in the introductory part of claim 17 for controlling a pressure medium operated actuator.

In the- prior art there is known, from the Finnish patent publication 91554, a method and apparatus for controlling a pressure medium operated actuator. This method utilizes a regulating unit and a valve system. When the regulating unit is in operation, the control members are moved in order to manipulate the valve arrangements of the valve system, so that the pressure medium is free to proceed in and out of the actuator and to influence by its pressure the actuator, moving its outlet, whereafter the motion of the actuator outlet is fed back to the regulating unit. Said method is characterized in that the motion of the control members affecting the valve arrangements of the valve system is realized as a linear motion, and that from the outlet of the actuator, the motion is fed back as linear motion to the regulating unit, so that the feedback motion affects in the opposite direction with respect to the linear motion of the control members of said regulating unit, and as a result the motion of the control members is essentially eliminated, in which case they continue manipulating the valve arrangements of the valve system from their shifted position, so that the pressure medium is free to proceed to the actuator during the operation of the regulating unit and to manipulate it with its pressure, and that the stopping of the regulating unit causes the linear feedback motion of the actuator to have a transfer effect to the control members, whereupon they are returned to their original position, and their control effect ends with the valve arrangements of the valve system, and the actuator is stopped.

Said arrangement for controlling a pressure medium operated actuator comprises a regulating unit and a valve system. The means for feeding the actuator motion back to the regulating unit are connected at the actuator outlet to the control members of the regulating unit in order to move them in a linear fashion. The linear motion of the control members, created by means of a motor element belonging to the regulating unit, is eliminated by linear feedback motion in the opposite direction, when the motor element is being used, and as a result the motion of the control members is stopped. Now the control members are in a transfer position where they still affect the valve arrangements of the valve system, so that the pressure medium is free to proceed during the operation of the motor element to the actuator and to manipulate it with its pressure. The stopping of the motor element causes the feedback motion of the actuator to have a transfer effect over the control members in order to return them to the original position, and the control effect to either of the valve arrangements to end, in which case the actuator stops.

Each of the two valve arrangements includes a number of valves whereby the proceeding of the pressure medium in and out of the actuator is regulated. There are four of these valves. The first valve is arranged in between the actuator and the pressure medium tank in order to regulate the outflow of the pressure medium.

The second and third valve are in mutual cooperation. The second valve is arranged in between the pressure medium tank and the third valve in order to control the third valve. The second valve is mampulated by moving the control members of the regulating unit. The third valve is arranged in between a pressure medium pump or a similar pressure medium source and the actuator in order to regulate the pressure medium feed flow. The fourth valve is arranged in connection with the third valve, in between the pressure medium pump or similar source and the second valve. By means of this valve, the first and third valve are closed after the control effect of the control members on the second valve has ended.

A drawback with the above described system is that both valve arrangements include many valves, so that they form a complicated mechanical structure. Moreover, a multi-step valve system leads to defects, such as delays in the operation of the actuator. This also results in that the adjusting accuracy of the actuator suffers. However, it is pointed out that the limits of the speed and adjusting accuracy only become apparent with long back and forth repeated transfer routes of a hydraulic cylinder piston and with high piston velocities, for instance.

An object of the invention is, among others, to eliminate the above described problems of the valve arrangement. A particular object of the invention is to realize a new, advanced valve arrangement and valve system, whereby pressure medium operated actuators can be accurately controlled. The advanced valve arrangement of the invention is characterized by the novel features enlisted in the appended patent claim 1.

The advanced valve arrangement according to the invention for controlling a pressure medium operated actuator, said valve arrangement being installed in between a pressure medium source, such as a pump, and a return tank or similar surge tank, comprises two matched and cooperating valves as well as control members, the first of said valves including a stem fitted in the valve box, which stem regulates the flowing of the pressure medium from the pressure medium source via the feed channel and the first actuator channel to the actuator, and via the second actuator channel and the outflow channel back to the pressure medium surge tank, and every second valve is arranged as the control valve of the first valve.

According to the invention:

- the valve box of the first valve, together with the stem fitted therein, is divided, in the stem shifting direction, to at least two parts: the front space of the valve box plus the front part of the stem, and the rear space of the valve box plus the rear part of the stem, so that the maximum transversal area of said front space of the valve box and front part of the stem is smaller than the maximum transversal area of said rear space of the valve box and rear part of the stem; - in the rear space and respectively in the front space of the valve box there is provided a narrowing spot, where there is fitted a first and respectively a second seat;

- the pressure medium feed channel and the first actuator channel are arranged, in the stem shifting direction, on different sides of the first seat, and the pressure medium outlet channel, which is connected to the outflow channel, as well as the second actuator channel, are arranged on different sides of the second seat;

- in the rear part and respectively front part of the stem, there is arranged a narrowing spot provided with a counterpart for the first and respectively the second seat, said counterparts and seats being fitted to be closely connected in the closed position of the valve;

- in the rear and front part of the stem, there are arranged a first and respectively a second connecting channel, whereby the pressure medium feed channel and the first actuator channel, and respectively the pressure medium outlet channel and the second actuator channel are connected in the open position of the valve; - the pressure medium source is connected, by a connecting channel, to the rear space of the first valve, so that the stem of the first valve is arranged to be pressed, by the pressure of the pressure medium, to the closed position, where the first and second connecting channels are closed, and simultaneously the flowing of the pressure medium through the first valve, via both the feed and outflow channels, is prevented; - the second valve is connected to the by-pass channel provided in between the rear space of the first valve and the tank, and

- the control members are arranged in connection with the second valve in order to control the second valve and thereby the first valve and the whole valve arrangement, and in said valve arrangement, when the second valve is opened, the by-pass channel from the rear space of the first valve to the pressure medium surge tank is opened, and the pressure in the rear space of the stem of the first valve decreases, so that the first valve opens owing to the pressure manipulating the valve box through the pressure medium feed channel, and the pressure medium is free to flow from the pressure medium source to the actuator through the feed channel, the first connecting channel and the first actuator channel, and from the actuator back to the pressure medium surge tank through the second actuator channel, the second connecting channel and the outflow channel.

An advantage of the invention is the structure of the first valve of the valve arrangement, owing to which this valve can be opened and closed under the control of the control valve, i.e. the second valve, by utilizing the pressure of the pressure medium.

Another advantage of the invention is that in the valve arrangement, by regulating a small pressure medium flow (the second, i.e. control valve), a large pressure medium flow (the first valve) of the actuator can be controlled.

A further advantage of the invention is that by means of the valve arrangement and the valve system based thereon, there can be established a simpler, more accurate and more reliable control of a pressure medium operated actuator.

Yet another advantage of the invention is that there can be realized a pressure medium operated, advantageously hydraulic, control arrangement including a short closed pressure medium system. In structure, this closed system is simple and suited to a limited space. Yet another advantage of the invention is that the actuator can be accurately controlled, even with high operation speeds.

Moreover, an advantage of the invention is that the tendency of the valve arrangement to vibrate is essentially eliminated.

Yet another advantage of the invention is that both the valve arrangement and the valve system can be controlled digitally by means of a suitable transfer device, for instance a stepping motor.

Furthermore, it is an advantage of the invention that the valve arrangement and the valve system can easily be modified for pressure medium operated actuators of various sizes, such as hydraulic cylinders and hydraulic motors.

The invention is explained in more detail below, with reference to the appended drawings, wherein

figure 1 illustrates a valve arrangement according to the invention in partial lengthwise cross-section; figure 2 illustrates the cross-section B-B of the valve arrangement of figure 1 ; figure 3 illustrates the cross-section C-C of the valve arrangement of figure 1 ; figure 4 illustrates the cross-section D-D of the valve arrangement of figure 1 ; figure 5 illustrates a second valve arrangement according to the invention in partial lengthwise cross-section; figure 6 illustrates a third valve arrangement according to the invention in partial lengthwise cross-section; figure 7 illustrates a fourth valve arrangement according to the invention in partial lengthwise cross-section; figure 8 illustrates a valve system according to the invention for controlling a pressure medium operated actuator, seen in partial lengthwise cross- section; and figure 9 illustrates a valve system and a hydraulic cylinder controlled thereby in partial lengthwise cross-section.

An advanced valve arrangement 1 according to the invention for controlling a pressure medium operated actuator 4 is illustrated in figure 1. The valve arrangement 1 is fitted in between a pressure medium source, such as a pump P, and a return tank T or a similar pressure medium surge tank. The valve arrangement 1 includes a pressure medium feed channel 2, which is connected to the pump P, and a pressure medium outflow channel 3, which is connected to the tank T in order to remove the pressure medium. The tank T is connected, by a channel, to the suction end of the pump P. The valve arrangement also includes two actuator channels 5; 6, which are connected to the pressure medium operated actuator 4.

The valve arrangement 1 is provided with two matched and cooperating valves 7, 8. The first valve 7 is arranged in between the pump P and the tank T in order to regulate the input and output flows of the pressure medium of the actuator 4, passing through the actuator channels 5, 6. The second valve 8 is arranged in connection with the first valve 7, in between the pump P and the tank T, in order to control the first valve 7.

The first valve 7 comprises a jacket 9, a valve box 10 and a stem 1 1. Inside the jacket 9, there is advantageously provided an elongate and cylindrical valve box 10. The stem 11 is fitted in the valve box 9, where it can be shifted most advantageously in the lengthwise direction A-A of the valve box. The stem 11 regulates the flowing of the pressure medium from the pressure medium source P through the feed channel 2 and through the first actuator channel 5 to the actuator 4, and through the second actuator channel 6 and outflow channel 3 back to the pressure medium surge tank T. In the drawings the flowing directions of the pressure medium are indicated by arrows.

The valve box 10, together with the stem 11 fitted therein, is divided, in the shifting direction A-A of the stem 11 , to at least two parts: to the first part of the valve box, i.e. to the front space 12, and to the second part, i.e. the rear space 13. The maximum transversal area of the front space 12 of the valve box is smaller than the maximum transversal area of the rear space 13 of the valve box. Advantageously the valve box 10 i cylindrically symmetrical, so that the maximum diameter d_emax of the front space 12 (cf. figure 5) is smaller than the maximum diameter d_tmax of the rear space 13 of the valve box. In each space 12, 13 of the valve box, there is arranged a narrowing spot, where the transversal area of the valve box space, and particularly the diameter d_emax, d_tmax is reduced: d_sl -> d_yl; d_s2 -» d_y2 (d_sl < d_tmax, d_s2 < d_emax). Moreover, said transversal areas and diameters d_sl , d_yl, d_s2, d_y2 are reduced towards the front end of the valve box. The narrowing spots form the first seat 310 of the rear space 13 of the valve box and the second seat 31 1 of the front space 12 of the valve box. The pressure medium feed channel 2 and the first actuator channel 5 are arranged on different sides of the first seat 310 in the second part of the valve box, i.e. in the rear space 13. Respectively, the pressure medium outlet channel 14 and the second actuator channel 6 are arranged on different sides of the second seat 31 1 in the first part of the valve box, i.e. in the front space 12.

The valve box 10 is provided in the jacket 9 of the valve arrangement 1 , as is illustrated in the embodiment of figure 6. As an alternative, the valve box 10 can be arranged in an auxiliary housing 30, which is then fitted in the jacket 9 of the valve arrangement 1 , in an auxiliary housing space 31 , as will be explained in more detail below (cf. figures 1-4, 5, for instance). In both cases, the valve box 10 and the stem 11 are most advantageously similar in structure; like numbers for like parts are used in the drawings.

Apart from the valve box 10, the stem 11 is divided, in the shifting direction A-A of the stem 11 , to at least two parts with different maximum transversal areas: to the first or front part 28 of the stem and to the second or rear part 29 of the stem. Said transversal areas of the stem 11 correspond to respective transversal areas of the valve box 10 (adjustments provided). Both the valve box 10 and the stem 11 are advantageously cylindrically symmetrical, in which case the maximum diameter of the front part 28 of the stem corresponds to the maximum diameter d_emax of the front space 12 of the valve box 10, and it is smaller than the maximum diameter of the rear part 29 of the stem, which corresponds to the maximum diameter d_tmax of the rear space 13 of the valve box (cf. figure 5).

Each stem part 29, 28 is provided with a sealing area 110, 111 , where there is fitted a sealing ring 15, 16, an adjusting channel 171 , 181 of the actuator channel 5, 6, a counterpart 312, 313 of the seat and a connecting channel 17, 18. The maximum transversal area of the front part 28 of the stem falls on the second sealing area 11 1 , and the maximum transversal area of the rear part 29 of the stem falls on the first sealing area 110. The sealing rings 15, 16 are fitted in sealing grooves 150, 160, which are located in the sealing areas 110, 1 11. When moving the stem 11 , the sealing rings 15, 16 slide against the inner surfaces of the front space 12 and the rear space 13 of the valve box 10 on the stem trajectory from the closed position to the open position and vice versa.

The adjusting channel 171 , 181 of the actuator channel 5, 6 is an annular channel next to the sealing area 110, 1 1 1 , whereto the actuator channel 5, 6 is connected when the valve 7 is in closed position. The counterpart 312, 313 of the seat is arranged in between the adjusting channel 171 , 181 of the actuator channel and the connecting channel 17, 18. The seats 310, 31 1 of the valve box 10 are arranged to be accurately matched with the counterparts 312, 313, when the valve 7 is in closed position (figures 1 , 5, 6 and 7). Respectively, in between the seats 310, 311 and the counterparts 312, 313 there are formed flow apertures 320, 321 , when the valve 7 is in open position, and the feed channels 5, 6 are via said apertures 320, 321 connected to the connecting channels 17, 18 and further to the feed channel 2 and the outlet channel 14. The diameter d_sl, d_s2 of the stem 1 1 at the adjusting channel 171 , 181 of the actuator channel 5, 6 is larger than the diameter d_yl , d_y2 at the connecting channel 17, 18. Said diameters d_sl , d_s2; d_{y l} , d_v2 are smaller than the maximum diameters d_tmax, d_emax of the corresponding stem part 28, 29 (figure 5).

The surfaces of the circular seats 310, 311 of the valve box 10 are advantageously conical surfaces, like the respective surfaces of their counterparts 312, 313, as is illustrated in figures 1 , 5, 6 and 7, among others.

The first valve 7 includes a first and second connecting channel 17, 18. The first connecting channel 17 is arranged in connection with the stem 11 , in between the sealing rings 15, 16, in the rear part 29 of the stem, near the second or rear end of the stem. By means of this connecting channel 17, the pressure medium feed channel 2 is connected, in the open position of the valve 7, to the first actuator channel 5. The length of said connecting channel 17 in the motional direction of the stem corresponds to the distance between the pressure medium feed channel 2 and the actuator channel, added with the summed-up width of the channels in the shifting direction of the stem. Thus the first connecting channel 17 extends from the vicinity of the first sealing ring 15 to the counterpart 312 of the first seat. The second connecting channel 18 of the first valve 7 is provided in the front part 28 of the stem 11. It extends from the counterpart 313 of the second seat of the stem 1 1 to the first end, i.e. the front end of the stem.

The structures of the first and second connecting channels 17, 18 are advantageously as is described below.

The first connecting channel 17 includes a first annular connecting channel part 33, whereto the end of the feed channel 2 is always connected, irrespective of the position of the stem 11 on its path in the valve box 10. Through the annular connecting channel part 33, the pressure of the pressure medium manipulates the stem 11 , pushing it towards the rear space 13 of the valve box 10, when the second valve 8 (120 in figure 6) is opened.

The first connecting channel 17 of the first valve 7 is provided with a number of first groove-like connecting channel parts 36, spaced apart on the circumference of the stem 11 , in parallel to the stem path and the axis A-A, which parts 36 are at their first end connected to the annular first connecting channel part 33, their second ends being connected, in the direction of the stem radius (i.e. on a plane perpendicular to the surface of the stem which is round in cross-section), to the outer surface of the stem by curved parts 37. The curved parts 37 connect, via the aperture 320, the first actuator channel 5 and the annular adjusting channel 171 further to the first connecting channel parts 36, to the first annular connecting channel part 33 and to the feed channel 2, when the valve 7 is in open position.

The second connecting channel 18 advantageously includes a number of second groove-like connecting channel parts 38, spaced apart on the circumference of the stem 11 , in parallel to the stem path and the axis A-A, which parts 38 open at their first end, at the end of the front part 28 of the stem 11 , towards the outlet channel 14 and the outflow channel 3. At the other end the second connecting channel parts 38 are connected in the direction of the stem radius (i.e. on a plane peφendicular to the surface of the stem which is round in cross-section), with curved parts 39 to the outer surface of the stem 11 , in the vicinity of the circular counteφart 313 of the second seat. The curved parts 39 connect, via the aperture

321 , the second actuator channel 6 and the annular adjusting channel 181 to the outlet channel 14 and further to the outflow channel 3, when the valve 7 is in open position.

The connecting channels 17, 18 of the type described above are flow-technically advantageous; the pressure medium flows remain as laminar as possible, and there is no turbulence. This also eliminates possible vibration tendencies of the stem 11. Moreover, the groove-like channel parts 36, 38 improve the adjusting properties of the valve 7; the flowing of the pressure medium through the valve 7 can be accurately adjusted.

The pump P is connected, with a control channel 19, to the rear space 13 of the valve box 10 of the first valve 7. Thus the stem 11 of the first valve 7 is arranged to shift, owing to the pressure of the pressure medium, to closed position, where the first and second connecting channels 17, 18 are closed, and at the same time the flowing of the pressure medium through the first valve 7 via the feed and outflow channels 2, 3 is prevented.

The second valve 8, 55, 120 (cf. figures 1 , 5 and 7) is arranged as the control valve of the first valve 7. Obviously the second valve can be realized in many different fashions. It is required that the flow-through of the second valve can be adjusted, and thus the operating speed of the first valve can be affected. An advantageous suggestion for the structure of the second valve is described below.

In the embodiment of figure 1 , the second valve 8 comprises a valve box 20 and a closing member 21 fitted therein, which closing member 21 is by means of a spring member 22 or the like arranged to close the valve flow-through channel, i.e. the valve box 20, so that the flowing of the pressure medium is prevented in the closed position of the valve. The flow-through channel of the second valve 8 is arranged to communicate with the by-pass channel 23 in between the rear space 13 of the first valve 7 and the outflow channel 3.

Advantageously the second valve 8 is connected to the stem 11 of the first valve 7, so that the second valve 8 is movable simultaneously and parallelly with the stem 11. The spring-loaded closing member 21 of the second valve 8 is arranged to function in the direction of the trajectory of the stem 1 1 of the first valve 7.

In the most advantageous embodiment, the second valve 8 is fitted coaxially, i.e. on the axis A-A in the stem 11 of the first valve 7, as is illustrated for instance in figures 1 and 7.

In the stem 1 1 of the first valve 7, there is provided a hole in the direction of its trajectory and the axis A-A, which at the front and rear end of the stem 1 1 forms a by-pass channel 23, and in the middle of the stem constitutes the flow-through channel of the second valve 8, i.e. the valve box 20. The closing member 21 and spring member 22 of the second valve are fitted in through the rear end of the stem 1 1 and locked in place by means of a screw sleeve 24, in the middle whereof there is provided a hole 25 parallel to the axis A-A, said hole being part of the by-pass channel 23. The stem 1 1 is provided with a seat 26 and aperture 27, which communicates with the by-pass channel 23. The closing member 21 rests, pressed by the spring member 22, against the seat 26 and closes the aperture 27 when the second valve 8 is in closed position (as is illustrated for instance in figure 1 ). In another embodiment of the valve arrangement, the second valve 120 is arranged outside the first valve 7, as is illustrated in figures 5 and 6. In structure this valve 120 is essentially similar to the second valve 8 provided in connection with the stem 1 1 in figure 1, and like numbers for like parts are being used. Now the second valve 120 is connected to the by-pass channel 121, which connects the rear space 13 of the valve box 10 of the first valve 7 to the outflow channel 3.

Advantageously the first valve 7 comprises a sleeve-like auxiliary housing 30, as is illustrated in the embodiments of figures 1-4, 5 and 7. The auxiliary housing 30 is fitted in the auxiliary housing space 31 of the valve arrangement jacket 9 and provided with sealings 305, 306, 307, 308 in the shifting direction of the axis A-A and the stem 1 1 , both externally and in between the feed channel 2 and the actuator channels 5, 6. By means of the auxiliary housing 30, a suitable form is obtained for the valve box 10. The auxiliary housing 30 and the stem 1 1 are accurately matched with each other. Their matching is realized for instance by grinding their contact surfaces in a common grinding process. From the point of view of producing the first valve 7, this is an advantageous production-technical solution. At the same time, in the auxiliary housing 30 there are arranged adjusting channels connected to the feed channel 3 and the actuator channels 5, 6, as will be explained below. By means of said adjusting channels, the operation of the valve is stabilized for example so that the stem 1 1 of the first valve 7 is subjected to an even pressure of the pressure medium from all surrounding directions. The auxiliary housing 30 and the stem 1 1, as well as the parts connected thereto, are most advantageously cylindrically symmetrical with respect to the axis A-A.

The auxiliary housing 30 is stepped in the direction of the axis A-A, with respect to both its inner and outer diameter, so that it is most advantageously provided with three sleeve-like auxiliary housing parts 301, 302, 303 having different diameters

(cf. figures 2-4). The outer diameter D₃ of the front end of the auxiliary housing, i.e. that of the third auxiliary housing part 303, is smaller than the outer diameter Dj of the rear end, i.e. the first auxiliary housing part 301. The outer diameter D₂ of the second auxiliary housing part 302 belonging to the middle part of the auxiliary housing is in between said outer diameters D_b D₃, so that D] > D₂ > D₃. The mutual relations of the inner diameters d_b d₂, d₃ of the auxiliary housing parts 301, 302,

303 are respectively: d, > d₂ > d . Moreover, the auxiliary housing part 303 of the front end of the auxiliary housing 30 includes a narrowing part 304, provided with an aperture which communicates with the outlet channel 14 of the first valve and has a diameter d₄ = d_y2 < d₃. The maximum diameter d_emax of the front space 12 of the valve box 10 of the first valve 7, and respectively the diameter of the front part 28 of the stem 1 1 at the sealing ring 15, corresponds to the inner diameter d₃ of the third auxiliary housing part 303 of the auxiliary housing 30 (clearances provided), and it is smaller than the maximum diameter d,_max of the rear space 13 of the valve box 10, and respectively the diameter of the rear part 29 of the stem 1 1 at the sealing ring 16, said diameter corresponding to the inner diameter di of the first housing part 301 of the auxiliary housing 30 (clearances provided). This arrangement provides for the movements of the stem 1 1 into closed position and respectively into open position (dotted lines in figure 1, among others) by means of the pressure of the pressure medium affecting the rear space 13 and respectively the first connecting channel 17 thereof.

The structure of the stem 1 1 is described above, and it is independent of the fact whether an auxiliary housing 30 is utilized in the embodiment (cf. for example figure 5) or not (cf. figure 6). In addition to this, the stem 1 1 includes two cylindrical sealing areas 110, 11 1, in which areas the sealing rings 15, 16 are fitted in suitable sealing grooves. When moving the stem 1 1, the sealing rings 15, 16 slide against the advantageously cylindrical inner surfaces of the first and third auxiliary housing parts 301, 303. The auxiliary housing 30 is provided with two circular seats 310, 31 1, the first 310 whereof is installed in between the inner surfaces of the first and second auxiliary housing parts 301, 302 with different diameters d_b d₂, and the second 31 1 is installed in the narrowing part 304 of the auxiliary housing 30, essentially at the front end of the auxiliary housing 30, in between the third auxiliary housing part 303 and the narrowing part 304, these two having different diameters d₃, d_y2 (= d ). The stem 1 1 is provided with circular counteφarts 312, 313 corresponding to the seats 310, 31 1. The surfaces of the circular seats 310, 31 1 are advantageously inclined conical surfaces, like the countersurfaces of their counter¬ parts 312, 313, and they are accurately fitted to conform to each other in the closed position of the valve 7.

The first seat 3 10 and the corresponding aperture 320 belong to the rear space 13 of the valve box 10 of the first valve 7. The feed channel 2 and the first connecting channel 17 are connected to the seat 310 and the aperture 320, as is the first actuator channel 5. The second seat 31 1 and the corresponding aperture 321 belong to the front space 12 of the valve box 10 of the first valve 7, particularly to the end of the front space 12. The second actuator channel 6, the second connecting channel 18 and the outflow channel 3 are connected to the aperture 321 by intermediation of the outlet channel 14. The circular counteφarts 12, 313 rest against the seats 310, 311 when the first valve 7 is in closed position, and close the flow apertures 320, 321 bordered by the seats 310, 31 1.

The first connecting channel 17 of the first valve 7 is arranged in connection with the stem 1 1, and it is advantageously formed according to the specification above. The connecting channel 17 includes a first annular connecting channel part 33, whereto the ends of the feed channel 2 are connected. The end of the feed channel 2 is shaped as an annular channel 34, which is fitted on the circumference of the sleeve-like auxiliary housing 30, particularly on that of the middle part 302 thereof, as is illustrated in figures 1-4 and 5. In the annular channel 34, there are radially provided apertures 35, which pass through the auxiliary housing 30 and lead to the rear space 13 of the valve box 10 and further to the first connecting channel 17, particularly to the connecting channel part 33 of the first annular channel. Through the annular connecting channel part 33, the pressure of the pressure medium manipulates the stem 11, pushing it towards the rear space 13 of the valve box 10, when the second valve 8 is opened.

The end of the first actuator channel 5 is shaped as an annular channel 341, which is arranged on the circumference of the first auxiliary housing part 301 of the auxiliary housing 30. In the annular channel 341, there are radially provided apertures 342, which pass through the auxiliary housing 30 and lead to the rear space 13 of the valve box 10 and further either through the aperture 320 to the first connecting channel 17 or to the first annular adjusting channel 171, depending on the position of the stem 11. On the other side of the adjusting channel 171, there is located the circular counteφart 312 of the first seat, which is pressed against the seat 310 belonging to the auxiliary housing 30 when the valve 7 is in closed position, and respectively they are set apart and the aperture 320 is open when the valve 7 is in open position.

The second connecting channel 18 of the first valve 7 is provided in connection with the stem 1 1. The second connecting channel 18 is located at the front end 28 of the stem 1 1. The second connecting channel 18 is advantageously formed as was explained above. The end of the second actuator channel 6 is shaped as an annular channel 344, which is arranged on the outer circumference of the third auxiliary housing part 303 of the auxiliary housing 30, as is illustrated in figures 1-4 and 5. In the annular channel 344, there are radially provided apertures 345, which pass through the valve housing 30 and lead to the front space 12 of the valve box 10 and further, either through the aperture 321 to the second connecting channel 18 or to the second annular adjusting channel 181, depending on the position of the stem 1 1. On the other side of said adjusting channel 181, there is located the circular counter¬ part 313 of the second seat, which counteφart 313 is pressed against the second seat 31 1 belonging to the auxiliary housing 30 when the valve 7 is in closed position, and respectively they are set apart and the aperture 321 is open when the valve 7 is in open position.

The valve box 10 of the first valve 7 includes a shoulder 52 or corresponding obstruction. The stem 1 1 of the valve 7 is arranged to move in the valve box 10, so that its motion is stopped at this shoulder 52, when the valve 7 is in a totally open position. The valve box 10 and the rear space 13 are bordered by said shoulder 52. As a continuation of the valve box 10 and the rear space 13, in the motional direction of the stem 1 1 and parallel to the axis A-A, there is provided an end space 53. In this embodiment, the diameter of the end space 53 is smaller than the diameter of the rear space 13, and the shoulder 52 is formed therebetween by means of a difference in measure. Through the end space 53, the rear space 13 is pressurized, i.e. pressure medium is fed therein through the control channel 19.

In between the rear space 13 of the first valve 7 and the pump P, there is advantageously provided a throttle 40, as is illustrated in figure 1, among others. Said throttle is arranged in the control channel 19.

In a preferred embodiment, the throttle 40 includes a threaded throttle pin 41 , which is fitted in a throttle nest 42 provided with corresponding threadings. In the middle of the throttle pin 41 , in the lengthwise direction thereof, there is drilled a hole 43 with a small diameter. The throttle nest 43 is compactly covered with a lid, such as a throttle cap 44, which can advantageously be opened and closed with a tool. The piupose of the throttle 40 is to reduce the pressure medium flow-through via the control channel 19, particularly when the second valve 8 is in open position. In that case the pressure medium flows via the control channel 19 to the rear space 13 of the first valve 7 and further through the second valve 8 to the outflow channel 3 and back to the tank T. When required, the throttle pin 41 can be unscrewed out of the throttle nest 42 and replaced by another throttle pin. The diameter of the hole 43 of the new throttle pin 41 can be chosen so that it deviates from the diameter of the hole of the previous pin. Thus the quantity of the pressure medium flowing therethrough can be chosen to be suitable. This affects, among others, the operating speed of the valve arrangement and the flowing of the pressure medium through the valve arrangement. As an alternative, instead of the throttle 40, the control channel 190 can be designed to have such a cross-section that the pressure medium flow in the by-pass channel is of the desired quantity, when the valves 7, 8 are in open position (cf. figure 5).

The control members 45 of the valve arrangement I advantageously include an electrically operated transfer device 46, a control axis 47 and a control pin 48 provided in the free end of the axis 47 (cf. figures 1, 5 and 7). The transfer device 46 moves the control axis 47 and the control pin 48 on a linear path. The control axis 47 is fitted in the axial space 49 of the jacket 9. In the axial space 49, the control axis 47 is supported with one or several bearings 50 against the jacket 9 of the valve arrangement. Moreover, the control axis 47 is provided with a sealing 54. The bearing 50 enables the linear motion of the control axis 47. In addition to this, the control members 45 include a control unit 51 for electrically controlling the electrically operated transfer device 46. The electrically operated transfer device 46 includes for instance an electric motor, such as a stepping motor, and a screw and nut motion converter in order to convert rotary motion into linear motion of the control axis 47 and the control pin 48.

The stem I I of the first valve 7 has two extreme positions: closed position, where the first counteφart 312 of the stem 1 1 rests against the first seat 310 and the second counteφart 313 rests against the second seat 311 (as is illustrated for instance in figure 1), and open position, where the end 29 of the stem 1 1 rests against the shoulder 52, and flow apertures 320, 321 (illustrated by dotted lines) are opened in between the counteφarts 312, 313 and the seats 310, 31 1. These correspond to the closed and open positions of the valve arrangement 1.

Let us observe for example the valve arrangement 1 of figure 1. Let us first assume that the first valve 7 is in closed position. The transfer device 46 moves, under the control of the control unit 51, the control axis 47 and the control pin 48 into direction E, and presses the closing member 21 of the second valve 7 against the spring load. Now the channel 23 from the rear space 13 of the first valve 7 through the outflow channel 3 to the tank T opens, and the pressure in the rear space 13 is rapidly reduced. Owing to the pressure of the pressure medium manipulating the stem 1 1 via the annular connecting channel 33, the stem 1 1 is shifted towards the shoulder 52, so that the first valve 7 is opened. Now the pressure medium is free to flow from the pump P to the actuator 4 through the feed channel 2, the first connecting channel 17 and the first actuator channel 5, and from the actuator 4 back to the tank T via the second actuator channel 6. the second connecting channel 18 and the outflow channel 3. At the same time the stem 1 1 moves together with the second valve 7 and the closing member 21 thereof in the direction of the trajectory of the control pin 48, i.e. of the axis A-A, and thus keeps the control pin 48 in controlled contact with the closing member 21.

The length of the controlling motion of the control pin 48 of the control members 45 defines how much the stem 1 1 of the first valve 7 is opened and how much it opens the apertures 320, 321. Respectively, the extent of the controlling motion adjusts the degree of throttling the first connecting channel 17 (respectively the second connecting channel 18) of the stem 1 1 and of the first actuator channel 5 (respectively the second actuator channel 6), i.e. the flowing of the pressure medium to the actuator 4 (out of the actuator 4). Thus pressure medium is fed into the actuator 4 and discharged therefrom in a controlled fashion.

When the control pin 48 has been sufficiently moved by the transfer device 46, the stem 11 of the first valve 7 is shifted to its extreme position against the shoulder 52. Now the first valve 7 and also the valve arrangement 1 are in a completely open position.

When the control pin 48 is shifted, by the transfer device 46, in the opposite direction F in relation to the one explained above, the second valve 8 begins to close and the stem 1 1 of the first valve begins to move towards closed position in a similar fashion but in an opposite order in relation to what was described above. The stem 1 1 reaches closed position, when the control pin 48 is shifted sufficiently far out of the stem 1 1.

When the second valve 120 is arranged outside the first valve 7, as in the embodiments of figures 5 and 6, the valves 120, 7 are in principle operated as was described above. However, a significant difference is the fact that in between the first and second valves 120, 7 there is not provided such an immediate feedback mechanism for intensifying the regulation as in the embodiment of figure 1 , for instance, where the adjusting of the second valve 8 manipulates the first valve 7, and simultaneously, along with the shifting of the stem 1 1 of the first valve 7, also the opening/closing stage of the second valve 8 is affected.

The transfer device 46 can also be realized as a mechanical lever device known as such, whereby the control axis 47 and the control pin 48 are shifted. In that case a separate control unit 51 is not needed. By means of a mechanical lever device. which is arranged to be part of the control unit 51, it is also possible to control the electrically operated transfer device 46 and therethrough the valve arrangement 1.

Figure 7 illustrates another valve arrangement 55 according to the invention, and like numbers for like parts with the valve arrangement 1 of figure 1 are being used. The second valve 8 is coaxially fitted in the stem 11 of the first valve 7, like in the valve arrangement 1 of figure 1. In this embodiment, the second valve 8 includes an auxiliary housing 56, inside which there are fitted the proper parts of the second valve arrangement 8 according to figure 1, such as the by-pass channel 23, the valve box 20, the closing member 21, the spring member 22 and the screw sleeve 25. The auxiliary housing 56 is fitted in the auxiliary housing space 57 provided in the stem 1 1 of the first valve 7a. The position of the auxiliary housing 56 is adjustable in the direction of the trajectory A-A of the stem 1 1.

Most advantageously the auxiliary housing 56 and the auxiliary housing space 57 are provided with matching threadings 58. By winding the auxiliary housing 56 with a suitable tool, such as a screwdriver, its position in the direction of the trajectory of the stem 11 can be modified and adjusted. The puφose is to remove any possible clearance from between the control members 46, particularly from between the control pin 48 and the closing member 21 when setting the valve arrangement into operating condition.

In figure 1 the actuator 4 is controlled by the valve arrangement 1, which in this embodiment is a double action hydraulic cylinder 60. Said cylinder 60 includes a piston 61, a piston rod 62 and a cylinder space 63. The piston 61 divides the cylinder space 63 into two parts: the first part 64 and the second part 65. The arrangement also includes a valve 66, such as a 4/2 valve or the like, whereby the operating direction G, R of the cylinder is changed. The control unit 51 controls the transfer device 46 of the valve arrangement 1 and the valve 66. Moreover, the system includes a position detector 67 for detecting the position of the piston 61 and the piston rod 62. The position detector 67 is connected to the control unit 51.

The valve 66 has two operating modes; in the first mode the actuator channels 5, 6 of the first side, i.e of the valve arrangement 1, and the connecting channels 66a, 66b of the second side, i.e. of the hydraulic cylinder 60 are directly interconnected: 5 -> 66a and 6 -» 66b, and in the second mode crosswise: 5 - ^■ 66b and 6 -» 66a. The double action hydraulic cylinder 60 is controlled by the valve arrangement 1 as follows. Let us assume that the valve arrangement 1 is in closed position, as is illustrated in figure 1, i.e. pressure medium does not flow therethrough. Now the piston 61 of the cylinder 60 is locked in some intermediate position in between the extreme positions of its trajectory, as is illustrated in figure 1. This intermediate position is known in the control unit 51 owing to the message sent by the position detector 67.

The piston 61 and particularly the piston rod 62 of the cylinder 60 are desired to be shifted in the direction G for the length of a predetermined path a. Now there is sent a command via the control unit 51 in order to realize the shift. According to the command of the control unit 51, the valve 66 is set into first operating mode (cf. above), and an operating command is sent for the control members 45. Now the transfer device 46 begins to shift the control axis 47 and control pin 48 towards the closing member 21 of the second valve 8 of the valve arrangement 1 (direction E) in order to open said closing member 21, with the above described results. When the first valve 7 is in open position, pressure medium is shifted, from the pump P via the feed channel 2 and the valve arrangement 1 to the first actuator channel 5 and further, via the valve 66 and the channel 66a, to the cylinder space 64 of the first side of the hydraulic cylinder 60. Owing to the influence of the pressure medium, the piston 61 is shifted in the direction G. Simultaneously pressure medium is let out of the second cylinder space 65 of the piston 61 through the channel 66b and the valve 66 as well as through the valve arrangement 1, to the outflow channel 3 and the tank T. When the piston 61 reaches the predetermined position, i.e. it has been shifted for the length of the path a, this is detected in the position detector 67, and information to that effect is sent to the control unit 51. Now the control unit 51 immediately sends a command to the control members 45 and their transfer device 46, which starts shifting the control axis 47 and the control pin 48 away from the closing member 21 of the second valve 8 of the valve arrangement 1 (direction F) in order to close said closing member 21 in the fashion described above. When the first valve 7 is in closed position, pressure medium does not flow from the pump P via the valve arrangement 1 to the hydraulic cylinder 60, nor therefrom to the tank T.

When the piston 61 of the hydraulic cylinder 60 should be shifted in the other direction R. the valve 66 is set into second operating mode, where the channels 66a and 6, and respectively the channels 66b and 5, are interconnected, i.e. said channels are cross-connected with respect to the first operating mode of the valve 66. Thereafter the valve arrangement 1 is used in exactly the same fashion as was described above. However, pressure medium is now fed from the pump P via the feed channel 2 and the valve arrangement 1 to the actuator channel 5, and via the valve 66 further to the channel 66b and therefrom to the second cylinder space 65 of the cylinder 60, and pressure medium is discharged from the first cylinder space 64 of the cylinder 60 via the channel 66a, the valve 66, the actuator channel 6 and the valve arrangement 1 to the outflow channel 3 and the tank T. The piston moves in the direction R.

It is pointed out that the valve arrangement according to the invention, such as the valve arrangement according to figures 1 and 5, can be directly used for controlling a single action hydraulic cylinder or the like, where the returning of the cylinder piston is arranged to take place by means of a spring. However, in the piston return step the pressure medium must then be returned to the tank T for instance through the return channel 6 and a valve, such as the valve 66, in principle in the same fashion as was explained above, but without feeding pressure medium into the actuator, i.e. to the single action hydraulic cylinder.

Figure 8 illustrates a valve system according to the invention for controlling a pressure medium operated actuator.

The valve system comprises two valve arrangements la and lb. The fust valve arrangement l a is like the one illustrated in figure 1, and the second valve arrangement lb is like the one illustrated in figure 7. Both are fitted inside a common housing 70. Each valve arrangement la, lb has a pressure medium feed channel 2a; 2b connected to the pump P or to a similar pressure medium source. Respectively, the valve arrangements la, lb have a common pressure medium outflow channel 3, which is connected to the tank T or to a corresponding pressure medium surge tank in order to remove pressure medium from the valve system. The tank T is connected, by means of a channel, to the suction end of the pump P. Two actuator channels 5a, 5b; 6a, 6b lead from each valve arrangement l a, lb to the pressure medium operated actuator 71.

The actuator channels 5a, 6b are coupled together and connected to the first side of operation of the actuator 71 in order to move the outlet 72 of the actuator in one direction G, and respectively the actuator channels 5b, 6a are coupled together and connected to the second side of operation of the actuator 71 in order to move the outlet 72 of the actuator in another direction R. Each valve arrangement la, lb includes two valves. The first valve 7a; 7b is fitted in between the pump P and the tank T in order to adjust the input and output flow of the pressure medium in the actuator 71. The second valve 8a, 8b is fitted in connection with the first valve 7a, 7b, in between the pump P and the tank T, in order to control the first valve 7a, 7b. The structure of the valve arrangement la corresponds to the structure of the valve arrangement according to figure 1. Like numbers for like parts of the valve arrangement 1 a and the valve arrangement 1 of figure 1 are being used, the formed provided with an additional letter a. The structure of the valve arrangement lb corresponds to the structure of the valve arrangement of figure 7, and like numbers for like parts are being used, but provided with an additional letter b.

The control members 73 of the valve system include a transfer device 74 and its control unit 88. The position detector 97 of the actuator outlet 72 can also be considered to belong to the control members 73.

The transfer device 74 includes a motor element, advantageously a stepping motor 75, and provided in connection thereto, a control axis 76, a motion converter such as a screw and nut motion converter 91 and a lever device 77. The axis of the stepping motor 75 is connected to the control axis 76, which is rotated thereby. The motion converter, such as the screw and nut motion converter 91, converts the rotary motion of the control axis 76 into linear motion. The stepping motor 75 is supported in connection with the clutch space 83. Inside the clutch space 83, there is provided a clutch 89 in order to switch the axis of the stepping motor 75 to the first end 76a of the control axis 76. By intermediation of the clutch 89, the rotary motion of the stepping motor 75 is transferred onto the control axis 76, so that also a slight back and forth movement of the control axis 75 is also allowed. The control axis 76 is fitted in the axial space 78. In the axial space, the control axis 76 is supported by two bearings 79, 80 to the housing 70. The bearings 79, 80 also allow an axial motion of the control axis 76. The insertion of the first end 76a of the control axis 76 via the aperture 81 to outside the housing 70 is provided with a sealing 82. The second end 76b of the control axis 76 is supported, by the bearing 80, to the housing 70 at the other end of the axial space 78.

The lever device 77 of the transfer device 74 is attached to the control axis 76 by means of a lever housing 84a. Advantageously the lever housing 84a is a cylindrical member, which is movably installed in the axial space 78. The lever housing 84a is attached, by means of holders 85a, 85b onto the axis 76. The lever housing 84a is free to move, together with the axis 76, when said axis is moved in linear fashion in the axial space 78. The control axis 76 can rotate is the middle of the lever housing 84a, in the aperture 85 proceeding in the lengthwise direction thereof. The lever housing 84a includes a protrusion 84b, which is arranged to protrude from the lever housing 84a and the axis 76, advantageously on a vertical plane in relation to the axis. At the free end of the protrusion 84b, there are provided a first and a second pin 86, 87. Each pin 86, 87 is formed of a bar. The pins 86, 87 are advantageously formed of a uniform straight bar passing through the protrusion 84b, so that the pins

86, 87 are located at opposite ends of the bar. In this case said bar and simultaneously the pins 86, 87 are essentially parallel with the lengthwise axis of the control axis 76 and the main axis A-A of the valve arrangements la, lb.

The valve arrangements la, lb of the valve system are arranged in connection with each other to form a cooperating unit. The two valves 7a, 7b; 8a, 8b of both valve arrangements are fitted in connection with the intermediate space 90. This inter- mediate space 90 is part of the outflow channel 3, and it is connected to the tank T. The axial space 78 is connected to the intermediate space 90. The lever housing 84 a is arranged in the axial space 78 so that the protrusion 84b extends to the inter¬ mediate space 90. The lever housing 84a can slide in linear fashion in the axial space 78 along with the control axis 76, and simultaneously the protrusion 84b can slide in the intermediate space 90.

The valve arrangements la, lb, particularly the first valves 7a, 7b, in connection with the stems I la, l ib whereof there are provided the second valves 8a, 8b, are arranged on different sides of the intermediate space 90, so that the trajectories of the stems I la, l ib are located on the same straight line, i.e. on the axis A-A. Now the stems I la, 1 lb of the first valves 7a, 7b are moved coaxially in the valve boxes 10a, 10b. The lever device 77 of the transfer device 74 is installed in the inter¬ mediate space 90, so that the pins 86, 87 are located in between the stems I la, l ib of the first valves 7a, 7b and the closing members 21a, 21b of the second valves 8a, 8b, and so that they are moved in the direction of the trajectory of the stems 1 la, 1 lb of the first valves 7a, 7b. Now the pins 86, 87 extend to the by-pass channels 23a, 23b and are located in the immediate vicinity of the closing members 21a, 21b of the second valves 8a, 8b when the first valves 7a, 7b are in closed position. In case there is a clearance in between the closing members 21a, 21b and the pins 86,

87, it is removed by adjusting the position of the auxiliary housing 56b of the valve arrangement lb in the direction of the trajectory of the closing member 21b of the second valve 8b, as was explained in connection with the description of figure 7. The actuator 71 is a double action pressure medium cylinder, advantageously a hydraulic cylinder. The piston 92 of the cylinder is fitted in the cylinder space 93. On one side of the piston 92, there is the first part of the cylinder space 93, i.e. the first cylinder space 94, and on the other side thereof there is the second part of the cylinder space 93, i.e. the second cylinder space 95. The piston rod 96 is connected to the piston 92, and it corresponds to the outlet 72 of the actuator. The first actuator channel 5a of the first valve arrangement la and the second actuator channel 6b of the second valve arrangement lb are connected to the first cylinder space 94 of the actuator 71, i.e. of the hydraulic cylinder. Moreover, the second actuator channel 6a of the first valve arrangement la and the first actuator channel 5b of the second valve arrangement lb are connected to the second cylinder space 95 of the actuator 71, i.e. of the hydraulic cylinder.

The operation of the valve system according to the invention is explained in more detail below, with reference to figure 8. The valve arrangements la, lb function as was described above, for instance in connection with figure 1.

Let us assume that the pump P is in operation and pressure medium is pumped into the valve system, to the feed channels 2a; 2b of the valve arrangements l a, lb. The pressurized medium proceeds, via the control channel 19a, 19b and the throttle 40a, 40b to the rear spaces 13a, 13b of the first valves 7a, 7b and closes these valves, i.e. pushes the stems I la, l ib into closed position. The pressurized medium cannot flow into the actuator 71 nor out thereof. The second valves 8a; 8b are also closed; the lever device 77 of the transfer device 74 is in its middle position (as is illustrated in figure 8) and the pins 86, 87 are in the vicinity of the closing members 21a, 21b, advantageously in contact with the closing members, but the second valves 8a, 8b are still closed.

The outlet 72 of the actuator 71, for instance the piston 92 and piston rod 96 of the hydraulic cylinder, should be shifted for the length of the trip s in the direction G. From the control unit 88, there is sent a command to operate for the transfer device 74, particularly to the stepping motor 75. Accordingly, the stepping motor 75 and the connected control axis 76 are started to rotate in the first rotary direction H. The screw and nut motion converter 91 converts the rotary motion of the control axis 76 into linear shifting motion, so that owing to the first rotary direction H, the control axis 76 and also part of the clutch 89a of the stepping motor are shifted in the direction I. The lever device 77 connected to the control axis 76 moves in the same direction therealong. The first control pin 86 starts to press the closing member 21a of the second valve 8a of the first valve arrangement la, and the second valve 8a is opened. The by-pass channel 23a in between the rear space 13a of the first valve 7a and the intermediate space 90 is opened.

In the embodiment according to figure 8, the actuator channel 5a of the first valve arrangement la is connected to the first cylinder space 94 of the hydraulic cylinder serving as the actuator 71. Consequently, the pressure medium flows into said cylinder space 94 and manipulates the piston 92 and the piston rod 96, shifting them in the desired direction G. The control unit 51 receives continuous information from the position detector 97 as for the location of the piston 92 and the piston rod 96. Simultaneously pressure medium is discharged from the actuator 71 via the second actuator channel 6a of the first valve arrangement 1 a. In the embodiment according to figure 8, the second actuator channel 6a is connected to the cylinder space 95 of the hydraulic cylinder serving as the actuator 71. Consequently, the pressure medium flows out of said cylinder space 95 while the shifting of the piston 92 reduces the cylinder space 95 and presses pressure medium out thereof, to the second actuator channel 6a. From the actuator channel 6a, the pressure medium is conducted to the second connecting channel 18a of the first valve 7a of the first valve arrangement la, and out of the valve box 10a via the outlet channel 14a and the intermediate space 90 to the outflow channel 3 and further to the tank T.

When the ste I la of the first valve 7a of the first valve arrangement la is shifted in the box 10a towards the rear space 13, i.e. towards the open position, the second valve 8a is shifted along with the stem I la. The lever device 77 of the control member, and particularly the control pin 86, keeps the second valve 8a open for a given transfer length of the stem 1 la. If said length is siupassed, the effect of the pin 86 to the closing member 21a of the second valve 8a terminates, and the second valve 8a is closed; pressure medium is again shifted into the rear space 13a of the first valve 7a via the control channel 19a and the throttle 40a, and it manipulates the stem I la by pushing it towards the closed position (direction L), i.e. by contracting the connecting channel 18a. At the same time the second valve 8a again enters the effective range of the control pin 86, and the situation is balanced out, i.e. the second valve 8a opens. A corresponding situation is repeated when closing the first valve arrangement la.

When the piston 92 of the hydraulic cylinder is shifted for a desired length s, this is detected by the position detector 97 in the control unit 51, and the transfer device 74, paiticularly the stepping motor 75, is sent a command to start rotating in an opposite direction, i.e. in the second rotary direction K. The rotary motion of the stepping motor 75 and the control axis 76 is converted by the screw and nut motion converter 91 into straight, linear shifting motion; owing to the second rotary direction K, the control axis 76 is shifted into the direction L. The lever device 77 connected to the control axis 76 and the first control pin 86 move therealong. The first control pin 86 starts to shift away from the closing member 21a of the second valve 8a, and the second valve 8a is closed. The by-pass channel 23a in between the rear space 13a of the first valve 7a and the intermediate space 90 is closed. The pressure of the pressure medium in the rear space 13a of the first valve increases, so that the stem 1 la is shifted towards the front space 12 into closed position; the first valve 7a is closed. The flow path of the pressure medium from the pump P into the feed channel 2a and via the first connecting channel 17a further to the first actuator channel 5a and to the actuator 71 , and respectively from the actuator 71 via the second actuator channel 6a and the second connecting channel 18a to the outflow channel 3 and the tank T are closed.

The stepping motor 75 is stopped when the control axis 76 and the first control pin 86 of the lever device 77 connected thereto is shifted to the original position (cf. the situation illustrated in figure 8), i.e. to a position where the first and second valve 7a, 8a are in closed position and the control pin 86 is in the immediate vicinity of the closing member 21a of the second valve 8a, even in contact with it. In this original position, also the second control pin 87 of the lever device 77 is respectively located in the immediate vicinity of the closing member 21b of the second valve 8b of the second valve arrangement lb.

During the operations described above, the first and second valves 7b, 8b of the second valve arrangement lb are in closed position, and pressure medium does not proceed in any direction through the valve arrangement lb.

When the direction of operation of the outlet 72 of the actuator 71 is wished to be changed in relation to what was described above, i.e. the hydraulic cylinder piston 92 should be shifted in the direction R, the stepping motor 75 is started to rotate from the original position in the second rotary direction K. The control axis 76 is now shifted, owing to the influence of the screw and nut motion converter 91, in the direction L. Now the control axis 76 of the control members and the second control pin 87 connected to the lever device 77 are used to manipulate the second valve 8b of the second valve arrangement lb in similar fashion as was explained above, in connection with the first valve arrangement la. The operation of the second valve arrangement lb is completely analogic to that of the above described valve arrangement la. The only difference is that the actuator channels 5b, 6b are cross- switched on opposite sides of the actuator 71, for instance on different sides of the hydraulic cylinder piston 92 in the cylinder spaces 94, 95, in order to change the operating direction of the actuator 71 into direction R.

During the operation described above, the first and second valve 7a, 8a of the first valve arrangement 1 a are in closed position, and pressure medium does not proceed in any direction through the valve arrangement 1 a.

Figure 9 illustrates a driving gear and an actuator, such as a hydraulic cylinder 103, controlled thereby. The driving gear includes control members 100, 101 and a valve system 102. The control members include a control unit 100 and a transfer device 101 to be adjusted thereby in order to control the operation of the valve system 102 and through it, the actuator 103. The valve system 102 comprises two valve arrangements la, lb, and they are advantageously similar as those illustrated in figure 8. In connection with the hydraulic cylinder 103 and the transfer device 101, there are also arranged means 104 for switching the motion of the actuator outlet, i.e. of the piston 107 of the hydraulic cylinder 103, back to the transfer device 101.

In structure the transfer device 101 corresponds to the transfer device 73 of the valve system in figure 8. The transfer device 101 comprises, as the transfer device proper, a motor element such as an electric motor, advantageously a stepping motor 75, and a control axis 76 and lever device 77 provided in connection thereto. The stepping motor 75 is connected, by means of the clutch 89, to the first end 76a of the control axis 76. The clutch 89 is fitted in the clutch space 83. The control axis 76 is fitted in the axial space 78, so that in addition to its rotary motion, also axial motion is allowed.

In connection with the control axis 76, there is provided a device for converting rotary motion into linear motion, which in this case is a screw and nut arrangement 91 (or a corresponding ball and nut arrangement). It is arranged at the other end 76b of the control axis 76. By means of the screw and nut arrangement 91, the rotary motion H, K transmitted to the control axis 76 of the stepping motor 75, is converted into linear motion of the control axis 76 in the lengthwise direction thereof, either in the direction I or L. To the control axis 76, there is connected the lever device 77, comprising a lever housing 84a and a protrusion 84b. The control pins 86, 87 are provided in connection with the protrusion 84b. By means of the control pins 86, 87. there is opened one of the valves 8a, 8b belonging to the first and second valve arrangement la, lb, and therethrough also the corresponding first valve 7a, 7b, as was explained in connection with figure 8.

In the embodiment of figure 9, the pressure medium cylinder, particularly the hydraulic cylinder 103, serves as the actuator. In known fashion, the cylinder 103 includes a piston 107, a piston rod 108 and a cylinder space 109. The piston 107 is arranged to move into the cylinder space 109. The piston 107 divides the cylinder space 109 into two parts; the first and second cylinder spaces 109a, 109b. The actuator channels 5a, 5b; 6a, 6b from both first valves 7a, 7b of the valve arrangements la, lb are cross-connected to the first and second cylinder space 109a, 109b, on different sides of the piston.

The feedback means 104 for switching the motion of the actuator outlet, such as that of the piston 107 of the hydraulic cylinder 103, back to the transfer device 101 comprise a screw and nut motion converter 106, an intermediate part 115 and a connecting part 105. By means of the feedback means 104, the linear motion of the piston 107 of the hydraulic cylinder 103 is converted into rotary motion. Said rotary motion is switched to the screw and nut motion converter 91 of the transfer device 101. By means of this arrangement, the rotary motion created by the stepping motor 75 is compensated, and the motion of the control axis 76 and the connected lever device 77 and control pins 86, 87 is stopped. The lever device 77 and the control pin 86, 87 remain in a position where they keep the first (or respectively the second) valve arrangement la (lb) in open position, and the piston 107 of the hydraulic cylinder 103 in continuous motion in the desired direction G, R.

In this embodiment the motion converter provided in connection with the hydraulic cylinder piston 107 for converting the piston's linear motion into rotary motion is realized by means of a screw and nut motion converter 106. The screw and nut motion converter 106 comprises a motion screw 1 13 and a motion nut 1 14. The piston 107 is connected to the motion screw 1 13 and this further with threadings to the motion nut 1 14. The motion nut 1 14 is connected to the intermediate part 1 15 and this further, via the connecting part 105 serving as a switch, to the screw and nut motion converter 91 of the transfer device 101. The piston 107 and the motion nut 1 13 are supported against the jacket 116 of the cylinder space 109, so that they are not allowed to rotate, when the piston 107 is shifted in the direction G, R of the axis of the cylinder space 109. Thus the linear shifting motion of the piston 107 and of the motion screw 113 is transmitted, by means of the threadings provided in between the motion screw 1 13 and the motion nut 1 14, to rotary motion N, Q of the motion nut 1 14 and further, via the connecting part 105, onto the screw and nut motion converter 91 of the transfer device 101, which in structure corresponds to the screw and nut motion converter 106 of said cylinder 107. (We also refer to the earlier Finnish patent application 91554 of the same applicant.)

The screw and nut motion converter 91 in turn converts the rotary motion N, Q into linear motion onto the control axis 76 of the transfer device 101. By means of this feedback rotary motion N, Q, the control axis 76 is shifted in the direction L, I, i.e. in a direction which is opposite to the linear motion created by means of the stepping motor 75. These motions in opposite directions L, 1 and I, L are matched so that they compensate each other, in which case the lever device 77 of the transfer device 101 remains essentially in place and tries to keep one of the second valves 8a, 8b of either of the valve arrangements la, lb of the valve system 102 continuously open, when the stepping motor 75 is in operation.

In principle the driving gear according to figure 9 for driving a hydraulic cylinder 103 or a similar actuator functions as follows. When the piston 107 or the hydraulic cylinder 103 and its rod 108 should be shifted into direction G (R), the stepping motor 75 is started through the control unit 100, and the motor is set to rotate in the direction H (K), so that the control axis 76 and the lever device 77 together with its control pins 86 (87) is shifted in the direction I (L). The second valve 8a of the first valve arrangement la is manipulated by shifting the control axis 76 and the control pin 86 in the first direction I, and the second valve 8b of the second valve arrangement lb is manipulated by shifting the control axis 76 and the control pin 87 into another, i.e. the opposite direction L. When manipulating the second valve 8a (8b) of the first (second) valve arrangement l a ( lb) by means of the control pin 86 (87), it opens together with the first valve 7a (7b), and pressure medium is conducted from the pump P via the feed channel 2a (2b) and the first valve 7a (7b) to the first actuator channel 5a (5b), and further to the first (second) cylinder space 109a (109b) of the hydraulic cylinder 103, in order to shift it into direction G (R). Pressure medium is discharged from the second (first) cylinder space 109b (109a) of the hydraulic cylinder 103 through the second actuator channel 6a (6b) and the first valve 7a (7b) further to the outflow channel 3 and to the tank T. When the motion of the piston 107 of the hydraulic cylinder 103 is desired to be stopped, for instance after a transfer path of a given length, the control unit 100 commands the stepping motor 75 to stop. The stopping of the stepping motor 75 results in that the piston 107 of the hydraulic cylinder 103 does not stop imme- diately, but is for a short moment shifted further, and thus causes an opposite feedback motion to the control axis 76; now the stepping motor 75 does not rotate the control axis 76 nor compensate the feedback rotary motion. As a result, the controlling effect of the control axis 76 and the control pin 86, 87 of the lever device 77 over either of the valve arrangements la, l b of the valve system 102 is terminated, which causes the motion of the piston 107 of the hydraulic cylinder to stop.

By means of a pulse sensor 1 17, the rotary motion of the connecting part 105, or in general that of the hydraulic cylinder motion converter 106, is observed. It is arranged to serve as the position detector of the piston 107 of the hydraulic cylinder 103, and it sends information to the control unit 100. On the basis of the information obtained from the pulse sensor 1 17, the position of the piston 107 is checked (or the information can be used for calibrating the position data of the piston). The position data proper of the piston 107 is observed directly from the control unit 100; on the basis of the information as to the rotary direction and control pulses (step pulses) given to the stepping motor 75, the position of the piston 107 or that of the outlet of a corresponding drive gear can be directly calculated, even without the position detector.

When the first valve arrangement la, lb is in closed position, no pressure medium flows therethrough, and the piston 107 of the hydraulic cylinder 103 - or the outlet of a corresponding drive gear - cannot move; medium is contained in both cylinder spaces 109a, 109b of the hydraulic cylinder 103.

In the embodiments of figures 8 and 9 described above, the actuator can, instead of a hydraulic cylinder, be a hydraulic motor or a corresponding pressure medium operated rotary actuator or an actuator producing linear motion. In principle the rotary motion of a rotary actuator is controlled in the same fashion as the linear motion of the piston of a hydraulic cylinder. In this respect we re refer to the earlier Finnish patent application 91554 of the same applicant.

It is pointed out that the trajectories of the control members, such as the control axis 76, in the direction of the axis A-A are relatively short, for instance of the order of 5 mm or even less. Thus the control members, and particularly the control pins 86, 87, can extremely rapidly affect the respective second valves 8a; 8b of the first or second valve anangement la, lb of the valve system, and further the first valves 7a, 7b.

The transfer device, such as the motor element, advantageously a stepping motor, belonging to the control members, is controlled from the control unit. The control unit includes a data processing unit, the core of which is generally a microprocessor. The quantity of motion of the actuator, such as the length of the motion, or the degree of rotation or number of revolutions, can be set in the transfer device in advance, and its realization can be controlled for instance on the basis of the position information and/or motional information obtained for instance from the position detector. Many other programmable control anangements known as such are possible, too.

The invention is not restricted to the above described embodiments only, but many modifications are possible within the scope of the inventional idea defined in the appended claims.

Claims

1. An advanced valve anangement (1) for controlling a pressure medium operated actuator (71), said valve anangement being ananged in between a pressure medium source (P), such as a pump, and a return tank (T) or a conesponding pressure medium surge tank, said valve arrangement (1) comprising two matched and cooperating valves (7, 8) and control members (45), said first valve (7) being provided with a stem (1 1) fitted in a valve box (10) for regulating the pressure medium flow from the pressure medium source (P) via a feed channel (2) and a first actuator channel (5) onto the actuator (71) and via a second actuator channel (6) and outflow channel (3) back to the pressure medium surge tank (T), said second valve (8) being ananged as the control valve of the first valve (7), characterized in that

- the valve box (10) of the first valve (7) together with the stem ( 1 1) fitted therein is in the shifting direction (A-A) of the stem divided into at least two parts: the front space (12) of the valve box and the front part (28) of the stem, and to the rear space (13) of the valve box and the rear part (29) of the stem, the maximum transversal area of said front space (12) of the valve box and the front part (28) of the stem being smaller than the maximum transversal area of the rear space (13) of the valve box and the rear part (29) of the stem;

- in the rear space (13) and respectively in the front space (12) of the valve box, there is provided a nanowing spot, where a first and respectively a second seat

(310, 311) are installed;

- the pressure medium feed channel (2) and the first actuator channel (5) are ananged, in the stem shifting direction (A-A), on different sides of the first seat (310), and the pressure medium outlet channel (14), which is connected to the outflow channel (3), and the second actuator channel (6) are ananged on different sides of the second seat (31 1);

- in the rear part (29) and respectively the front part (28) of the stem, there is ananged a nanowing spot provided with a counteφart (312, 313) for the first and respectively the second seat (310, 311), said counteφarts and seats being fitted to be compactly matched in the closed position of the valve;

- in the rear and front part (28, 29) of the stem (1 1), there is provided a first and respectively a second connecting channel (17, 18), whereby the feed channel (2) of the pressure medium and the first actuator channel (5), and respectively the pressure medium outlet channel (14) and the second actuator channel (6) are interconnected in the open position of the valve (7);

- the pressure medium source (P) is connected, by means of a control channel ( 19), to the rear space (13) of the first valve (7), so that the stem ( 1 1 ) of the first valve (7) is ananged to be pressed, owing to the influence of the pressurized medium, to closed position, where the first and second connecting channel (17, 18) are closed, and simultaneously the flowing of the pressure medium through the first valve (7) via both the feed and outflow channels (2, 3) is prevented; - the second valve (8) is connected to a by-pass channel (23) provided in between the rear space (13) of the first valve (7) and the tank (T), and - the control members (45) are arranged in connection with the second valve (8), in order to control the second valve (8) and thereby the first valve (7) and the whole valve anangement (1), in which valve anangement (1), when the second valve (8) is opened, the by-pass channel (23) from the rear space (13) of the first valve (7) to the pressure medium surge tank (T) is opened, and the pressure in the rear space ( 13) of the stem (1 1) of the first valve (7) is reduced, so that the first valve (7) is opened owing to the pressure affecting the valve box ( 10) via the pressure medium feed channel (2), and pressure medium is free to flow from the pressure medium source (P) to the actuator (71) through the feed channel (2), the first connecting channel (17) and the first actuator channel (5), and from the actuator (71) back to the pressure medium surge tank (T) through the second actuator channel (6), the second connecting channel (18) and the outflow channel (3).

2. A valve anangement according to claim 1, characterized in that the second valve (8) includes a valve box (20) and a closing member (21) fitted therein, said closing member being ananged, by means of a spring member (22) or the like to close the valve; and that the control members (45) include a control pin (48) for manipulating the closing member (21 ) of the second valve (8) when adjusting the flow-through of the valve (8) and likewise when controlling the valve arrangement (1).

3. A valve anangement according to claim 2, characterized in that the second valve (8) is connected to the stem ( 1 1 ) of the first valve (7), so that the second valve (8) is movable parallelly with the stem ( 1 1), and that the spring-loaded closing member (21 ) is arranged to be operated in the motional direction of the stem ( 1 1) of the first valve.

4. A valve anangement according to claim 3, characterized in that the second valve (8) is fitted coaxially in the stem (1 1) of the first valve (7).

5. An advanced valve anangement according to claim 3 or 4, characterized in that the second valve (55) includes an auxiliary housing (56), inside which there are fitted a flow-through channel (23), a closing member (21) and a spring member (22), said auxiliary housing (56) being fitted in the stem (1 1) of the first valve (7), advantageously in a auxiliary housing space (57) provided in the direction of the trajectory thereof, and that the position of the auxiliary housing (56) in the motional direction of the stem ( 1 1) is adjustable (figure 7).

6. An advanced valve anangement according to claim 5, characterized in that in between the auxiliary housing (56) and the auxiliary housing space (57), there are provided threadings (58), so that by turning the auxiliary housing (56), its position in the direction of the trajectory of the stem (1 1) can be changed in order to remove clearance from between the control members (45), particularly from between the control pin (48) and the closing member (21 ).

7. A valve anangement according to claim 3, 4, 5 or 6, characterized in that the outlet channel (14) of the first valve (7) is ananged at the end of the front space (12) of the valve box (10), and the control pin (48) is fitted to proceed through the outlet channel ( 14) to the second valve anangement (8) provided in connection with the stem ( 1 1) of the first valve (7), said control pin (48) manipulating the closing member (21 ) of the second valve (8) when controlling the valve arrangement (1).

8. A valve anangement according to any of the preceding claims, characterized in that the first connecting channel (17) includes a first annular connecting channel part (33), whereto the feed channel (2) is connected, and wherethrough the pressure of the pressure medium manipulates the stem ( 1 1) of the first valve (7), pushing it towards the rear space (13), when the second valve (8) is opened.

9. A valve arrangement according to claim 8, characterized in that the first connecting channel (17) includes a number of first groove-like connecting channel parts (36) spaced apart on the circumference of the stem (11 ), in the direction of the stem trajectory (A-A), said parts (36) being at their first end connected to the annular first connecting channel part (33).

10. An advanced valve anangement according to claim 8, characterized in that the first groove-like connecting channel parts (36) are at their other end connected, in the direction of the stem radius, by curved parts (37) to the outer surface of the stem ( 1 1), in the vicinity of the circular counteφart (312) of the first seat.

11. A valve anangement according to any of the preceding claims, characterized in that the second connecting channel (18) includes a number of second groove-like connecting channel parts (38), spaced apart on the circumference of the stem (1 1) and parallel to the stem axis (A-A).

12. An advanced valve anangement according to claim 1 1, characterized in that the second groove-like connecting channel parts (38) are at their other end connected, in the direction of the stem radius, by curved parts (39) to the outer surface of the stem (1 1), in the vicinity of the circular counteφart ( 13) of the second seat.

13. A valve anangement according to any of the preceding claims, characterized in that the first valve (7) includes a sleeve-like auxiliary housing (30) fitted in the jacket (9) of the valve anangement, by means of which auxiliary housing (30) the valve box (10) is suitably shaped, and that said auxiliary housing (30) and stem (1 1) are mutually matched.

14. A valve anangement according to claim 13, characterized in that in the sleeve-like auxiliary housing (30), there are ananged adjusting channels (341, 342; 34; 35; 344, 345) connected to the feed channel (2) and the actuator channels (5, 6).

15. A valve anangement according to any of the preceding claims, characterized in that the surfaces ofthe seats (310, 311) of the valve box (10) of the first valve (7) are conical surfaces, as well as the countersurfaces of their counteφarts (312, 313) of the stem (1 1).

16. A valve anangement according to any of the preceding claims, characterized in that in between the rear space (13) of the first valve (7) and the pressure medium source (P) in the control channel (19), there is ananged a throttle (40).

17. An advanced valve system (70) for controlling a pressure medium operated actuator (71), said valve system being fitted in between a pressure medium source, such as a pump (P), and a tank (T) or conesponding pressure medium surge tank, characterized in that the valve system (70) comprises two matched valve arrangements (la, lb) according to any of the preceding claims, each of said valve anangements including a first valve (7a, 7b) and a second valve (8a, 8b) provided m connection with the stem (I la, l ib) of said first valve, said valve anangements being ananged coaxially (A-A) on opposite sides of an intermediate space (90), so that the outlet channel (14a, 14b) of the valve box (10a, 10b) of the first valve (7a, 7b) of each valve anangement opens to the intermediate space (90) and further to the tank (T), and that the control members (73) include two control pins (86, 87), which are movably ananged in the intermediate space (90), so that they affect, one by one, via the outlet channel (14a, 14b) to the closing member (21a, 21b) of the second valve (8a, 8b) of the valve anangement (la, lb), against the spring load, in a case where the stem (I la, l ib) of the first valve is wished to be shifted from the closed position to the open position, and pressurized medium should be conducted onto one side of the actuator (71) and discharged from the other side thereof, in order to move the outlet (72) of the actuator in a desired direction.