A DEVICE FOR POSITION INDICATION FOR VALVE SLIDES

Abstract: The invention relates to an arrangement in a directional valve (1) having a valve slide (2) which can be moved between at least three positions, i.e. between at least one neutral position and at least two active, hydraulic flow positions. The position of an operating lever and/or a valve slide is indicated by breaking and making an output operating circuit (24) having electrical connector means (18, 19). In order to ensure that the valve slide will return to a neutral position after being moved away from its neutral position, there is provided a spring system (5) which forms a part of the operating circuit (24). In the neutral position of the valve slide, the circuit (24) is earthed (25) through the valve housing or a corresponding part and is closed between its connector means (18, 19). When the valve slide (2) is moved in one direction away from the neutral position, the operating circuit (24) is broken between earth and its one connector (18), whereas when the valve slide (2) is moved away from the neutral position in another direction, the operating circuit is broken between earth and its other connector (19).

Description: A DEVICE FOR POSITION INDICATION FOR VALVE SLIDES The present invention relates to an arrangement relating to hydraulic-motor directional valves of the kind which include a valve slide for indicating the position of an operating lever and/or slide by breaking and making an output manoeuvering ' circuit, said slide being adjustable between at least three positions, i.e. between at least one neutral position and at least two hydraulic flow active positions, wherein the ' arrangement includes a spring system which functions to ensure that the valve slide will return to a neutral position subsequent to being moved in a direction away from said neutral position. As with many other systems and arrangements, hydraulic systems are constructed and dimensioned for a given maximum load and there is normally incorporated in each hydraulic system some form of protection against over- loads, irrespective of whether the system, or arrange¬ ment, is mobile or stationary. Such overload protectors may have the form of one or more overflow or load relief valves which are included in the hydraulic circuit of the system and which open to conduct the flow of hydrau- lie medium to a tank immediately a pressure that is con¬ tingent on prevailing loads exceeds a predetermined consumer pressure value consumer. The consumers incorporated in the hydraulic system may comprise hydraulic motors, both rotating and linear motors, for instance hydraulic piston-cylinder devices. When a hydraulic piston-cylinder device is subjected to load, the moment arm of the load acting on the device at a particular moment in time may be such as to result in an overload when the hydraulic piston-cylinder device concerned is activated, so as to extend the moment arm of the load, but, on the other hand, not in those cases when the operator activates or controls the directional valve of the hydraulic piston-cylinder device concerned so that the moment arm of the load carried by the pis- ton-cylinder device will remain unchanged or is short¬ ened. Thus, in a manoeuvering situation, the operator can choose either one of two possible procedures for activating a relevant hydraulic motor via an associated directional valve, of which two choices one will be the correct choice with regard to avoiding the occurrence of an overload and the other will be the wrong choice and will result irrevocably in the occurrence of an over¬ load. Overloads, however, are states which are desirable to eliminate to the greatest possible extent, not least to avoid unnecessary breakdowns in the equipment used. In the case of known techniques, the occurrence of over¬ loads of the aforesaid kind are avoided by using so- called logic circuits which are coupled to a dump valve and which are so constructed as to ensure that when the valve slide of an associated directional valve is moved in a direction in which overloading can occur, the dump valve will be activated in order to conduct the flow hydraulic medium to the tank and therewith prevent hydraulic medium from flowing to the hydraulic piston- cylinder device controlled by the directional valve in question, therewith avoiding the occurrence of an over¬ load. So-called external components such as, for in¬ stance, microswitches or other position indicators which function to indicate the position and/or directional movement of the operating lever, and therewith the valve slide, have hitherto been used exclusively for deliver¬ ing to respective logic circuits information relating to the direction in which the valve slide of the direc- tional valve moves, and therewith to activate an associ¬ ated logic circuit. Such so-called external components. however, are difficult to fit and also require space, and, above all, also require highly accurate trimming and constant adjustment in order to function in the manner intended, resulting in high maintenance costs. The object of the present invention is therefore to provide an a lever and/or slide position indicating arrangement which is not encumbered with the troublesome deficiencies of the known arrangements, primarily with regard to trimming and subsequent adjustments, but which is so constructed as to be a) highly accurate, b) highly reliable and positive in operation, and c) can be readi¬ ly installed and used in all types of applications. A further object of the present invention is to obtain, with the aid of the inventive lever and/or slide posi¬ tion indicating arrangement an overload protector of the last mentioned type which is more reliable and more positive than the earlier known arrangements, and which can be fitted and used in a simpler fashion in all types of applications, and with which the logic circuits obtain an indication of the direction of movement of the slide or the operating lever. These objects are achieved with an inventive arrangement having the characteristic features set forth in the following Claims. In principle, the inventive arrange¬ ment for indicating the position of the lever and/or the slide is mainly characterized in that the return spring system is included as a part in the manoeuvering circuit which is earthed via the valve housing or the like and which has two connections, and which in the neutral position of the valve slide is closed, and which is broken between earth and the one connection when the valve slide is moved in said one direction away from its neutral position, and which is broken between earth and the other connection, when the valve slide is moved in the other direction away from said neutral position. The return spring system which functions to return the valve slide and the operating lever from, e.g., an active position to a neutral position forms part of the slide-position indicating manoeuver circuit in accor¬ dance with the present invention, and said manoeuver circuit is connected to the logic circuit of the hydrau¬ lic motor concerned in a manner to provide protection against an overload. The logic circuit contains, in a known manner, information or data which relates to the pressure created by the load acting on the hydraulic motor at a given moment in time, and which also relates to the latest direction of movement of the hydraulic motor and therewith information to the effect that an overload may occur if the moment arm or lever force of the load acting on the hydraulic motor is increased. Thus, the inventive arrangement informs the logic cir- cuit of the direction in which the valve slide moves, and the logic circuit decides whether movement of the valve slide in this direction is permitted or not, on the basis of this information or data. If movement of the valve slide in said direction is not permitted, the logic circuit will ensure that the dump valve is acti¬ vated so as to lead hydraulic fluid to the aforesaid tank instead of to the hydraulic motor, and in this way prevent the occurrence of an overload in a simple and effective manner. On the other hand, if the valve slide can be allowed to move in said direction, the logic cir¬ cuit will not activate the dump valve and the hydraulic fluid will instead pass to the hydraulic motor concerned. The inventive arrangement affords many advantages. One primary advantage is that no trimming is required at all, while still enabling the operating or manoeuvering circuit to be made and broken in a very quick and precise fashion. Furthermore, there is no hysteresis in the arrangement, and the arrangement requires no space, since the spring holder of the return spring system is used as an electric contact means. In addition, an extremely high contact pressure and an extremely large contact area is obtained. The present lever and/or slide-position indicating arrangement can also handle very large currents, is very easy to install, can be readily serviced and is inexpensive in operation, and also has an extremely long useful life and is very reliable in operation over the whole of its useful life. The present invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a side view, partly in section, of a hydraulic directional valve, and shows the valve in a neutral or closed position and provided with an inven- tive slide-position indicating arrangement; Figure 2 illustrates the arrangement in one active position of the valve; Figure 3 illustrates the inventive arrange¬ ment in another active position of the valve; Figure 4 is an end view as seen essentially in the direction indicated by the line IV-IV in Figure 1; Figure 5 illus¬ trates schematically a number of directional valves provided with the inventive arrangement and of which one is coupled to a logic circuit for a consumer included in a hydraulic mobile system; Figure 6 is a sectional view of a somewhat modified embodiment of the inventive arrangement; and Figure 7 is a sectional view of an embodiment of the inventive arrangement in which the valve slide of the directional valve is operated, or manoeuvered, with the aid of a servo-device or the like. In the drawings, the reference numeral 1 identifies generally a directional valve which may be included in a pack of such valves, as illustrated in Figure 5. The valve typically includes a valve slide 2 which is slide- ably mounted in its valve housing 3 for movement in the direction of its longitudinal axis and which can be dis¬ placed from a neutral or closed position, shown in Figure 1, in either one direction or the other to an active position by means of an operating lever 4, or in some other manual or mechanical fashion, for instance with the aid of a peddle, by hand, by means of a plung¬ er, with the aid of an electromagnet provided with two windings each operating in a particular direction, with the aid of an electric motor, by means of pressure, by means of pressure increases which are generated through the medium of a control valve, by electrohydraulic means with pressure lowering through the medium of a control valve, and with the aid of servo-devices, as illustrated schematically in Figure 7, and so on. The illustrated directional valve 1 is a triple-action valve, meaning that the valve slide 2 can be moved to any one of three different positions, namely a neutral or closed position, as illustrated in Figure 1, and two separate active positions in which hydraulic medium can flow to and from the hydraulic motor served by the directional valve concerned. One of these active posi¬ tions is shown in Figure 2 and is designated the A- position and may be one terminal position of valve slide movement, while the other active position is shown in Figure 3 and is designated the B-position and may be the other terminal position of valve slide movement. The illustrated inventive arrangement for indicating the position of the operating lever and/or the valve slide includes a known spring system 5 which functions to return the valve slide to its neutral position, said system including a spring 7 which is mounted between two generally cup-shaped holders 8 and 9. The bottoms 10 of the two holders face towards one another and are slide- ably mounted on a slide pin 12 having a head 11. The slide pin 12 is disposed concentrically with the longi¬ tudinal axis 13 of the slide, and in the case of the illustrated embodiment is formed integrally with the valve slide 2, although it will be understood that the slide pin 12 may be fastened to the valve slide 2 or connected thereto in any other way, even though this is not shown in the drawings. The slide pin 12 has an external diameter which is smaller than the outer diame¬ ter of the slide 2 and the outer diameter of the head 11, and thereby allows the two holders 8 and 9 on the slide pin 12 to move solely between the mutually facing end surfaces 14 of the head 11 and the slide 2. Each end-part of the two holders 7 and 8 remote from respec¬ tive bottoms 10 has outwardly facing, circumferentially extending support flanges 15 between which the spring 7 is held tensioned with a force such that it is able to return the two holders 7, 8 to the neutral position shown in Figure 1 when applicable, the holder bottoms 10 being held in abutment with the mutually facing end surfaces 14 of the head 11 and the slide 2 respectively and the support flanges 15 on respective holders is held against a respective electrically conductive member 16 in said neutral position. This is achieved because the two cup-shaped holders 7 and 8 together have a depth which is adapted to the distance between the mutually facing surfaces 17 of the electric contact members 16 and also to the distance between the mutually facing surfaces 14 of the head and the slide, so that, in said neutral position, the respective bottoms 10 of the holders 8, 9 are in abutment with the mutually facing surfaces 14 of the slide pin and each respective support flange 15 against its electric contact member 16, each of which is provided with an outwardly projecting elec¬ tric connectors 18, 19, for instance in the form of a connector pin. The two illustrated electrical contact members 16 of the illustrated embodiment have the form of plates and, on the side remote from the spring 7, are electrically insulated against the valve housing 3 and against an end-piece 21 through insulating plates 20. The end-piece 21 is anchored to the valve housing 3 by means of bolts 22. A sleeve 23 surrounding an inventive arrangement 5 is secured firmly to the valve housing 3 and is electrically insulated at its ends against both the valve housing 3 and the end-piece 21. When the valve slide 2 occupies its neutral position, the two contact plates 16 together with the holders 8, 9, the valve slide 2 and the headed slide pin 12, and also the spring 7 when said spring, similar to the holders 8, 9, the slide 2 and the slide pin 12, is made of an electrically conductive material, form a closed lever and/or slide-position indicating circuit 24 be¬ tween the connector pins 18, 19, said circuit being earthed through the slide 2 and the valve housing 3 at 25. When the valve slide 2 is moved by the lever 4, or in some other way, in the direction of the arrow 26 towards its one active position, i.e. position A, as shown in Figure 2, the slide pin 12 and its head 11 will entrain the holder 18, thereby causing the support flange 15 of said holder to leave the contact member 16 and therewith break the circuit 24 between the connector pin 18 of the contact member 16 and earth, as illustrat¬ ed in Figure 2. This takes place at a very early stage and long before the slide 2 is brought to an active position. At the same time as the holder 8 is moved, the spring 7 is also tensioned to an extent sufficient to be able to return the support flange 15 of the holder 8 into abutment with the electrical contact member 16 when the valve slide returns to a neutral position. When the valve slide 2 is moved in the direction of the arrow 27 (Figure 1) towards its other active position, i.e. position B, in response to movement of the operat¬ ing lever 4, or is moved in some other way, the valve slide 2 causes the holder 9 to move relative to the slide pin 12, therewith causing the support flange 15 of the holder 9 to move away from its contact member 16 and therewith break the circuit 24 between the connector pin 19 of the contact member 16 and earth 25, such as illus¬ trated in Figure 3. This also takes place at a very early stage and thus long before the slide 2 occupies an active position. As the holder 9 is moved, the spring 7 is also tensioned to an extent sufficient to return the support flange 15 of the holder 9 into abutment with its respective electric contact member 16, when the valve slide 2 returns to a neutral position. The circuit 24 thus provides a simple, but effective and reliable, indication of the direction in which the valve slide moves and the different positions of the valve slide, i.e. the neutral position and the two active positions A and B, and an effective overload protector for hydraulic motors is obtained when this slide-posi¬ tion indicating arrangement is used together with some form of known logic circuit or the like coupled to a dump valve, as will be evident from the following. Shown in Figure 5 is a pack of directional valves 1, of which some are shown provided with a device 5 for indi¬ cating the position of the valve slides in accordance with the present invention. The respective slide-posi¬ tion indicating circuits 24 of these directional valves are connected to said logic circuit in a coupling box 30, this logic circuit serving the hydraulic motor by means of which the jib or arm 32 of a crane is raised and lowered, said motor having the form of a hydraulic piston-cylinder device 31 in the Figure 5 illustration. A pressure sensor 33 delivers to the logic circuit information concerning the hydraulic pressure that prevails in the piston-cylinder device 31, said pressure sensor indicating the hydraulic pressure caused by the load P and its moment arm and impermissible movement in a direction away from a direction sensor 34, which in- eludes a pendulum 35, and which thus indicates whether or not movement in the moment-increasing direction is permitted. Also connected to the logic circuit is a dump valve 36 which when an overload is imminent is activated by the logic circuit and ensures that the pump pressure flow is led to the tank, therewith preventing the occur¬ rence of said overload. Since the logic circuit which coacts with the hydraulic piston-cylinder device 31 is of a known kind, it will not be described in detail here. Thus, when the slide- position indicating circuit 24 according to this inven¬ tion is connected to one such logic circuit, the slide 2 of the directional valve 1 is able solely to control the piston-cylinder device 31, when the risk of an overload is imminent, in a manner such as solely to move in a direction in which the moment arm of the load P is reduced or shortened. If, despite everything, the valve slide 2 is moved in the opposite direction, the hydrau¬ lic piston-cylinder device will not be affected because the circuit 24 will immediately be broken with the slide in this position and consequently no control signal can be sent to the hydraulic piston-cylinder device via the coupling box 30. As shown in Figure 6, the sleeve 23 which surrounds the spring 7 and the holders 8, 9 may be made of an insulating material and formed integrally with the end- piece 21, with one contact member 16 provided in the end-piece 21, for instance moulded therein. The valve slide 2 of the directional valve included in the embodi- ments illustrated in Figures 1-6 is manoeuvered by a lever and is returned to its neutral position from each of the two active positions by means of a spring. This return spring mechanism includes the spring 7 which is mounted actively between the support flanges 5 of its holder, so as to be able to return the valve slide 2 from each of said active positions to its neutral posi¬ tion shown in Figure 1. Figure 7 illustrates an embodiment in which the valve slide 2 is connected through the.slide pin head 11 to a piston, or plunger, 37 of known kind, conveniently a servo-device 38 which functions to move the valve slide 2 from and to its various positions, i.e. from its neutral position to one of the aforesaid active posi- tions, and vice versa. It will be understood that the invention is not res¬ tricted to the aforedescribed and illustrated embodi¬ ments thereof and that these embodiments can be modified and changed in many ways within the scope of the inven¬ tive concept defined in the following Claims. For exam¬ ple, the invention can be applied in many different fields than the aforedescribed. One example in this regard is that the invention can be applied advanta- geously in battery-driven trucks for starting the elec¬ tric motor of the hydraulic pump.

Claims: CLAIMS 1. An arrangement relating to hydraulic-motor direc¬ tional valves (1) of the kind having an adjustable valve slide (2) which can be moved between at least three positions, i.e. between at least one neutral position and at least two active hydraulic-flow positions so as to indicate the position of an operating lever and/or a valve slide, by breaking and making an output operating circuit (24) having electrical connector means (18, 19); said arrangement further including a spring system (5) which ensures that the valve slide will be returned to a neutral position after being moved in a direction away from said neutral position, c h a r a c t e r i z e d in that the spring system (5) forms part of the operat¬ ing circuit (24); and in that in the neutral position of the valve slide, the operating circuit (24) is earthed (25) via the valve housing or some like part, the oper¬ ating circuit (24) is closed between its connector means (18, 19), in that when the valve slide (2) is moved in one direction away from the neutral position, the oper¬ ating circuit (24) is broken between earth and its one connector means (18); and in that when the valve slide (2) is moved in the other direction away from said neutral position, the operating circuit (24) is broken between earth and its other connector means. 2. An arrangement according to Claim 1, in which each spring (7) in the spring system is mounted between two holders (8, 9) which are moveable in the neutral posi¬ tion, c h a r a c t e r i z e d in that in the neutral position of the valve slide, the holders (8, 9) abut electric contact plates (16) which are insulated in related to remaining parts and each of which is connect- ed with a respective operating circuit connector means (18, 19). 3. An arrangement according to Claim 1 or 2, c h a r ¬ a c t e r i z e d in that the operating circuit of the. arrangement is connected to a dump valve (36) or the like which is connected to a logic circuit which func- tions to detect the position of the operating lever and/or the valve slide, so as to prevent the occurrence of an overload.

Inventors: MARKLUND MARTIN, MARKLUND, MARTIN
Applicants: HYDRAUTO AB
Application year: 1992
Main classification: F15B15
IPC codes: F16K37