HYDRAULIC VALVE ARRANGEMENT

Abstract: The disclosure is directed to a seat valve arrangement (C4) for controlling a hydraulic oil flow to e.g. a linear or rotary hydraulic motor. The valve could be connected to a pump which acts as a pressure medium source. The arrangement of the present invention includes at least one seat valve (C4) located in a main flow connection, e.g. between the pump and the motor. Each seat valve (C4) would adjust the flow in the main flow connection via a pilot flow adjustable by a pilot valve (E4). The pilot flow originates from the main flow through the seat valve (C4).

Description: This invention relates to a seat valve arrangement for high pressure medium as hydraulic oil. Known valve means of this kind comprise at least one pressure-controlled valve, the control pressure of which is adjusted by means of a pilot control valve. These known pressure-controlled valves normally comprise a valve slide, which adjusts both the supply of pressure medium to the motor and the return flow from the same. These known valves, however, do not always meet the demand in question, owing to internal leakage which implies, for example, that a linear motor as a double-acting hydraulic cylinder is not actuated to carry out the desired movements. In GB-A-767 823 it is shown a valve arrangement comprising pilot operated seat valves, one thereof being located in a main flow connection between pump and an actuator and the other thereof being located in a return connection between the actuator and a tank. Each seat valve is of on/off type and is controlled to open position by causing the fluid-pressure in a valve chamber, behind the valve piston of the seat valve, to fall and to closed position under influence of a spring. Said pressure fall is obtained by opening a pilot valve in a passage connecting said valve chamber with the main flow connection. When closing said pilot valve the pressure increases in the valve chamber above the piston and said piston will close under influence of the spring. By this on/off valve arrangement it is not possible to control a hydraulic motor as to the speed as well as to the direction of the movement. The object of the present invention is to eliminate the above indicated disadvantages with known valve means, and to provide a valve arrangement which is fully flow controlled and functions as a proportionally controlled seat type valve with hydraulic feedback. This object is achieved in that the valve means according to the present invention has been given the characterizing features defined in the attached claims 1 and 3. The invention is described in greater detail in the following, with reference to the accompanying drawings, in which: Fig 1 is a schematic view of a section through a basic design of a valve means incorporating the seat valve arrangement, according to the invention for controlling a double-acting hydraulic cylinder, Fig 2 is a hydraulic diagram of the embodiment shown in Fig. 1, Fig 3 is a schematic view of a section of a first embodiment of a seat valve with associated pilot valve comprised in the valve means, and Fig 4 is a schematic view of a section of a second embodiment of a seat valve with associated pilot valve comprised in the valve means. The seat valve arrangement according to this invention is intended to be used in a valve means to control or adjust a hydraulic motor, which in the drawings generally is designated by 1, irrespective of whether it is a single- or double-acting linear motor, for example a cylinder, or a rotary motor, and the motor ports of which are designated by A and B. The valve means is coupled to the hydraulic circuit between the motor to be served by the valve means and a pump P acting as pressure medium source. The valve means is connected to a tank T, which in principle comprises a power valve part 2, a pilot valve part 3 and an operating part 4, which parts are assembled to one unit or section. Several such units in their turn can advantageously be assembled to a valve package for the control of several motors, as will be explained in greater detail further below. In Figs. 1 and 2 a basic embodiment of the present valve means for controlling a double-acting hydraulic cylinder 1 with two motor ports A and B is shown. At this embodiment, the power valve part 2 comprises four seat valves C1, C2,C3 and C4 mounted in a valve housing 2a, and a check valve D located in the same valve housing. The valve housing 2a further is formed with a connection P1 to the pump P, a connection A1 to the motor port A, a connection B1 to the motor port B, and a connection T1 to the tank T. The seat valve C1 is located as inlet valve in a supply or inlet passageway P1-A1 between the pump connection P1 and the motor port connection A1, and the seat valve C2 is located as inlet valve in a supply or inlet passageway P1-B1 between the pump connection P1 and the motor port connection B1. The seat valve C3 is located as outlet valve in a return flow passageway A1-T1 between the motor port connection A1 and the tank connection T1, and the seat valve C4 is located as outlet valve in a return flow passageway B1-T1 between the motor port connection B1 and the tank connection T1. The seat valves C, which advantageously can be designed, as they are shown in the drawings, as so-called cartridge units, i.e. each seat valve C comprises a movable valve cone 5 and enclosing the same a cartridge 6, which is stationary in the valve housing 2a and sealed against the same by O-rings 7, The seat valves are controlled each by a pilot valve E, which are connected to the respective seat valve by internal pilot flow channels in the valve housing. The pilot valves E further are collected in the pilot valve part 3, in pairs at the embodiment according to Fig. 1, and are actuated at this embodiment directly mechanically by an operating lever 8 comprised in the operating part 4. The pilot valve E1, more precisely, serves or controls the seat valve C1 and is connected thereto through a channel 9 and to the motor port connection A1 through a channel 10. The pilot valve E4 controls the seat valve C4 and is conneted thereto through a channel 11 and to the tank connection T1, and thereby to the tank T, through a channel 12. The pilot valve E2 controls the seat valve C2 and is connected thereto through a channel 13 and to the motor port connection B1 through a channel 14. The pilot valve E3, finally, controls the seat valve C3 and is connected thereto through a channel 15 and to the tank connection, and thereby to the tank, through a channel 16. When the operating lever 8 is not actuated, it is in the neutral position shown in Fig. 1. In this position all pilot valves are held closed, i.e. the conic balanced valve cone 17 of each pilot valve is held abutting its valve seat 19 by a compression spring 18. Hereby, due to the absence of a pilot flow through the pilot valves E, also all seat valves C are held closed for flow in the normal flow direction, for reasons which will become apparent from the following description of the present seat valve C both as inlet valve (Fig. 3) and as outlet valve (Fig. 4), in which applications the seat valve C acts in accurately the same way, but has differently shaped valve cones 5, depending on the flow direction. As shown in Fig. 3 where as in Fig. 4 the cartridge 6 is omitted for reasons of simplicity, and as mentioned before, the seat valve with its valve cone 5 is located in a main flow passageway P1-A1, and in this passageway, between the valve inlet P1 and the valve outlet A1, a valve seat 20 is located, against which the valve cone 5 is prestressed resiliently by a force in response to the pressure in the valve inlet P1, which force acts on the end surface 21 of the valve cone which is remote from the valve seat 20. Said end surface 21 is located in a space 22, which communicates both with the associated pilot valve E and with the valve inlet P1 through a cavity 23 in the cylindric valve cone 5 and at least one connecting channel 24 formed in the side of the valve cone. As also shown in Fig. 3, the valve seat 20 is formed with a cylindric wall 25 located radially outside the seat and enclosing the same. Said wall, which properly is formed in the cartridge 6 of the seat valve, extends axially away from the seat 20. Inside of the wall 25, the valve cone 5 which is shaped as a cylindric plunger is movable with sealing fit to the wall 25. In the wall 25 in the cartridge 6 at least one opening (not shown in the drawing) is located closest to the seat and forms a connection to the outgoing portion of the main flow passageway, in which the seat valve is located. The connecting channel 24 is so positioned and designed that it forms a throttling, the flow area of which increases with increasing distance of the valve cone 5 from its seat 20. At the embodiment shown in Fig. 3 this has been achieved in that the connecting channel 24 has been given the shape of two diametrically opposed ports of axially oblong shape, which ports extend from the inner cavity 23 to the shell surface of the plunger 5. The oblong ports 24 are located at such a distance from the valve cone surface intended to abut and seal against the valve seat 20, that the end of the ports 24 which is located farthest away from said surface is located slightly outside a set-off or an outermost radial end edge 27 of the cylindric wall 25 enclosing the valve cone 5. Hereby always, i.e. even when the valve cone 5 abuts its valve seat 20, a small connection for pressure medium from the valve inlet to the space 22 behind the valve cone 5 is formed, and hereby the pressure at completely closed pilot valve E will be the same in the space 22 as in the valve inlet. As the end surface 25 is greater than the end surface 28 of the cavity 23, thus, the valve cone 5 is held abutting its valve seat 20 and holds the seat valve C closed as long as the pilot valve E is closed and prevents a pilot flow to pass through. When, however, the pilot valve is actuated by means of the operating lever 8 for permitting a pilot flow to pass through, pressure medium flows through the throttled connecting channel 24, and the valve cone 5 hereby is caused to move from its seat 20 so much as is required for establishing balance between the pressure in the space 22 behind the valve cone 5, which pressure acts in closing direction on the valve cone, and the pressure of the pressure medium in the valve inlet P1. The valve cone 17 of the pilot valve here acts as an adjustable throttling, and the greater the pilot flow is which passes through the pilot valve, the farther away from its seat 20 extends the valve cone 5, and the greater is the main flow through the seat valve, and at fully opened pilot valve also maximum flow through the seat valve is obtained. It can be said in other words, that the main flow through the seat valve C is a copy of the pilot flow through the pilot valve enlarged in dependency on the differences in area between the pilot flow channels and main flow channels. The present seat valve C, thus, can be regarded as a flow amplifier. In reverse flow direction to the one shown in Fig. 3, the present seat valve can freely permit a flow to pass past the valve cone 5. This is an advantage in many practical connections, and as the valve cone 5 is not mechanically prestressed against its seat 20, for example by a compression spring or the like, the pressure drop in the reverse direction is very low, and in this flow direction the seat valve acts as a check valve easy to open and having,so to speak ,built-in anti-cavitation function. The present seat valve C, as has been mentioned, copies the flow characteristics of the associated pilot valve E with an amplifying factor independent of the nature of the characteristics, and hereby the seat valve is given a wide field of application. Another advantage of this seat valve is that the adjusting forces of the pilot valve E are very small because only a very small portion of the total flow is used as pilot flow through the pilot valve E. The present seat valve, thus, can be controlled with very small forces, which renders the valve easy to remote control, for example by means of electric signals or the like. As an outlet valve, as shown in Fig. 4, the seat valve is provided with a solid valve cone 5, which has no inner cavity 23, and the connecting channel 24 between the valve inlet B1 and the space 22 behind the valve cone 5 consists of at least one longitudinal notch or groove in the shell surface of the valve cone. In the closed position of the valve shown in Fig. 4, the end edge remote from the valve seat 20 of each such groove is located directly outside the outer radial end edge 27 of the cylindric wall 25 enclosing the valve cone 5 and extends from said end edge in the direction to its surface intended to abut the valve seat all the way inward to a portion 5a of the valve cone, which portion is located adjacent said surface and has a smaller diameter so as to form a passage, which via the opening or openings 26 in the cartridge 6 of the seat valves, which cartridge is not shown in Fig. 4, communicates with the return passageway B1, and hereby this passageway communicates with the space 23 behind the valve cone 5, which thereby is exposed on its end surface 21 to the same pressure as prevailing in the return passageway B1 and thereby is held abutting its valve seat 20 and closing the valve. With this valve cone, the seat valve has the same advantages and function as with the cone shown in Fig. 3. For operating the valve means according to the present invention, the operating lever 8, which in the Figures is shown rotatably mounted on an axle 30, is moved in one direction or the other. When the lever is moved to the right in Fig. 1, i.e. in the direction of the arrow 31, simultaneoulsy the two lower pilot valves E1 and E4 connected in series are actuated, i.e. these conic valve cones 17 are removed simultaneously from their respective valve seats 19. Hereby the channels 10 and 9 are connected to each other, so that a pilot flow responsive to the angle position of the operating lever is established through the pilot valve E1, which implies that the valve cone of the associated seat valve is moved in a corresponding degree from its seat 20 and connects the pump P with the motor port A, and also the channels 11 and 12 are connected to each other, so that a pilot flow also responsive to the angle of the position of the operating lever is established through the pilot valve E4, which implies that the valve cone 5 of the associated seat valve C4 is moved in a corresponding degree from its valve seat 20 and connects the motor port B to the tank T. Hereby, thus, a main flow determined by the degree of the position of the operating lever is obtained from the pump P via the seat valve C1 to the motor port A, and a similar return flow from the motor port B to the tank T via the tank connection T1 is obtained, and the plunger of the cylinder is caused to move in the direction marked by the arrow 32 in Fig. 1. When the operating lever 8 is moved in the opposed direction, i.e. in the direction marked by the arrow 33 in Fig. 1, the two upper pilot valves E2 and E3 connected in series are actuated simultaneously, i.e. these conic valve cones 17 are removed simultaneously from their respective valve seats 19. Hereby the pilot flow channels 14 and 13 are connected to each other whereby a pilot flow responsive to the angle of the position of the operating lever is obtained through the pilot valve E2, which implies that the valve cone 5 of the associated seat valve C2 is moved in a corresponding degree from its valve seat 20 and connects the pump P to the motor port B, and the pilot flow channels 15 and 16 are connected to each other, whereby a pilot flow also responsive to the angle of position of the operating lever is obtained through the pilot valve E3, implying that the valve cone 5 of the associated seat valve C3 is moved in a corresponding degree from its valve seat 20 and connects the motor port A to the tank T via the tank connection T1. Hereby, thus, a main flow determined by the angle of position of the operating lever is obtained from the pump P to the motor port B, and a similar return flow is obtained from the motor port A to the tank T, and, thus, the plunger of the cylinder is caused to move in the direction marked by the arrow 34 in Fig. 1. The valve means described in the foregoing is intended to be connected to a constant pressure source, for example a variable constant pressure controlled pump.

Claims: A seat valve arrangement (C4) for high pressure medium such as hydraulic oil, comprising a valve housing having a main return flow passage (B1-T1), a valve seat (20) surrounding the main return flow passage within the valve housing, a valve body (5) slidably located within a cylindric space (25) of the valve housing for movement from a closed position to an open position and being pilot operable by a pilot flow, a pilot flow chamber (22) located at the valve body end (21) remote from the valve seat (20), characterized in that the valve body (5) is pilot operable independent of the pressure through a variable pilot flow restriction (24,27), said variable pilot flow restriction comprising at least one channel (24) formed in the outer side of the valve body (5) and connecting the main return flow passage upstream of the valve seat (20) to said pilot flow chamber (22) for conveying pressure medium to said pilot flow chamber even when the valve body (5) is in its closed position abutting the valve seat (20), said channel (24) having a throughflow area which increases with increasing distance of the valve body (5) from the valve seat (20), and a first pilot flow passage (11) communicating the pilot flow chamber (22) with an inlet of a pilot valve (E4), and a second pilot flow passage (12) communicating an outlet of said pilot valve (E4) with the main return flow passage downstream of the valve seat (20), said pilot valve (E) having means (8) for gradually opening and closing said pilot valve to create a controllably pilot flow from the main return flow passage upstream of the valve seat (20) through the pilot flow chamber (22) and the pilot valve (E4) to said main return flow passage downstream of the valve seat for controlling the position of the valve body (5) and, thus, the main flow through the main return flow passage independent of the pressure and as a function of the pilot flow. A seat valve arrangement as claimed in claim 1, characterized in that the variable pilot flow restriction comprises two channels (24) located diametrically at the outside of the valve body (5). A seat valve arrangement (C1) for high pressure medium such as hydraulic oil, comprising a valve housing (2a) having a main supply flow passage (P1-A1), a valve seat (20) surrounding said passage within the valve housing, a valve body (5) slidably located within a cylindric space (25) of the valve housing for movement from a closed position to an open position and being pilot operable by a pilot flow a pilot flow chamber (22) located at the valve body end (21) remote from the valve seat (20), characterized in that the valve body (5) is pilot operable independent of the pressure through a variable pilot flow restriction (24,27), said variable pilot flow restriction comprising at least one channel (24) extending from the outside of the valve body to a cavity (23) within said body communication with the main supply flow passage upstream of the valve seat, said channel connecting the main supply flow passage upstream of the valve seat to said pilot flow chamber (22) for conveying pressure medium to said pilot flow chamber even when the valve body (5) is in its closed position abutting the valve seat, said channel (24) having a throughflow area which increases with increasing distance of the valve body (5) from the valve seat (20), and a first pilot flow passage (9) communicating the pilot flow chamber (22) with an inlet of a pilot valve (E1), and a second pilot flow passage (10) communicating an outlet of said pilot valve with the main supply flow passage downstream of the valve seat (20), said pilot valve (E1) having means (8) for gradually opening and closing said pilot valve to create a controllably pilot flow from the main supply flow passage upstream of the valve seat through the pilot flow chamber (22) and the pilot valve (E1) to said main supply flow passage downstream of the valve seat for controlling the position of the valve body (5) and, thus, the main flow through the main supply flow passage (P1-A1) independent of the pressure and as a function of the pilot flow. A seat valve arrangement as claimed in claim 3, characterized in that the variable pilot flow restriction (24,27) comprises two channels (24) located diametrically.

Inventors: ANDERSSON, BO
Applicants: ANDERSSON, BO
Application year: 1982
Main classification: F15B13
IPC codes: F16K31, G05D7, F15B13, F15B11