CONTROL VALVE

Abstract

Control valve (20) which is coupled to a hydraulic cylinder (18) for moving a lifting mast (12) forwards and backwards, wherein the lifting mast (12) serves to raise and lower a fork (11), wherein the control valve (20) moves a valve slide (30) in relation to a valve body (40) and thereby selectively connects a first passage (P) and a second passage (T) with an extension-side actuator port (B) and a retract-side actuator port (A), where high-pressure hydraulic oil is introduced through the first passage (P), and the second passage (T) leads into a low-pressure area, the extension-side actuator connection (B) serves to pre-tension a piston of the hydraulic cylinder (18) in the direction of a side on which the lifting mast (12) is moved forward, and the inward-facing actuator connection (A) serves to pre-tension the piston of the hydraulic cylinder (18) towards a side on which the lifting mast (12) is moved backwards, and wherein a recessed section (41) is formed on a web (31) in the valve slide (30), which blocks communication between the inlet-side actuator connection (A) and the second passage (T), and the recess section (41) has a shape in which the surface of an opening formed between the valve body (40) and the bridge (31) changes in two stages, wherein the exclusion section (41) has a first area, a second area, a third area and a fourth area, wherein in the first area the area of ​​the opening between the valve body (40) and the bridge (31) gradually increases, in the second area, which is connected to the first area, the area of ​​the opening between the valve body (40) and the bridge (31) is constant, in the third area, which is connected to the second area, the area of ​​the opening between the valve body (40) and the bridge (31) gradually increases, and in the fourth area, which is connected to the third area, the area of ​​the opening between the valve body (40) and the bridge (31) is constant, wherein a distance from a surface in the first region and a surface in the second region to the valve body (40) is defined as the first distance, and a distance from a surface in the third area and a surface in the fourth area to the valve body (40) is defined as the second distance, which is greater than the first distance, and wherein the first area and the third area have a semicircular shape in a top view, and where one dimension of the second area and the fourth area is the same in a lateral direction.

Description

BACKGROUND OF THE INVENTION Technical field

[0001] The present invention relates to a control valve coupled to a hydraulic cylinder that moves a lifting mast forwards and backwards in a reach truck, wherein the lifting mast serves to raise and lower a fork. Related technology

[0002] A reach truck is equipped to move a lifting mast, which raises and lowers a fork, in a forward-backward direction between a retracted state, which is a state in which the lifting mast is retracted, and an extended state, which is a state in which the lifting mast is extended forward.

[0003] In the reach truck, a control valve coupled to a hydraulic cylinder used to move the lifting mast is configured to move a valve spool relative to a valve body. This allows for the selective connection of a first passage, into which high-pressure hydraulic oil is introduced, and a second passage, which leads to a low-pressure area. An actuator port on the extension side pre-tensions a piston towards the side on which the lifting mast moves forward, and an actuator port on the retraction side pre-tensions the piston towards the side on which the lifting mast moves backward. Furthermore, the flow rate of the hydraulic oil in the control valve is regulated by a notch formed on a rib in the valve spool.

[0004] In the case of a reach truck, if it is abruptly stopped when an extension lever is actuated towards the extension side, and the truck is carrying a workpiece while moving, an inertial force is generated that causes the mast to move in the direction of the vehicle body. Because this force is transmitted to the hydraulic cylinder, the hydraulic cylinder's force, which limits the mast's position in the forward-backward direction, becomes unstable, resulting in a phenomenon where the mast and any forks it supports enter an unstable state.

[0005] Patent literature 1 discloses an extension control device of a reach truck, wherein the extension control device comprises an extension cylinder that causes a lifting mast to extend or retract, an oil control valve which, in response to actuation of a lever, adjusts a quantity of hydraulic oil that is supplied to the extension cylinder, a flow control valve which is arranged on an oil passage between the oil control valve and the extension cylinder, a vehicle speed detection element which detects a vehicle speed of the reach truck, a load detection element which detects a load carried by a fork, and a controller 5 which calculates and controls a constriction extent of the flow control valve by means of vehicle speed data from the vehicle speed detection element and load data from the load detection element.

[0006] JP 2001-271 803 A discloses a compact control valve with a spool and a valve body, wherein the spool is provided with webs and is longitudinally displaceable within the valve body to selectively connect a first pressure line and an oil tank passage with two actuator connection ports, with recessed sections formed on the webs. JP H08-192 761 A discloses a control valve with a cylindrical sleeve and a cylindrical spool that is axially movable within the sleeve. The sleeve includes two actuator connection ports to which a hydraulic cylinder is connected via an oil pump, and annular groove sections, each with vertical edges. The spool includes webs for sealing the flow through the actuator connection ports and recesses for connecting the actuator connection ports, the recesses being separated from each other by sections.The slide valve has edges at a boundary section between the recesses and the webs, which are formed in offset positions. US 2014 / 0026546A1 describes a regeneration valve for a hydraulic circuit with a valve element for controlling the flow, wherein the valve element has a flow slot configured such that the fluid exits the slot at an outlet angle that changes as the valve element moves between a first and a second position. [Literature of related technology][Patent literature]

[0007] Patent literature 1: Japanese patent disclosure no. JP 2000-53398A BRIEF SUMMARY OF THE INVENTION [Problems to be solved]

[0008] The extension control device disclosed in patent literature 1 must include not only the flow control valve, but also the vehicle speed detection element and the load detection element, which is why the device is not only expensive, but also has a complex design and configuration. Furthermore, the problem arises that the control system is not easy to implement.

[0009] The present invention was developed to solve these problems, and one object of the present invention is to provide a control valve which has a simple design and is able to stabilize a lifting mast even when a reach truck is abruptly stopped during an extension operation. [Means of solving the problems]

[0010] The claimed invention is defined in independent claim 1. The control valve according to the invention, which is coupled to a hydraulic cylinder for moving a lifting mast in a reach truck forwards and backwards, wherein the lifting mast serves to raise and lower a fork, moves a valve spool with respect to a valve body and thereby selectively connects a first passage, into which high-pressure hydraulic oil is introduced, and a second passage, which opens into a low-pressure area, to an extension-side actuator connection for pre-tensioning a piston of the hydraulic cylinder in the direction of a side on which the lifting mast is moved forwards, and to a retraction-side actuator connection for pre-tensioning the piston of the hydraulic cylinder in the direction of a side on which the lifting mast is moved backwards.A recessed section is formed on a bridge in the valve slide, which blocks communication between the inlet-side actuator connection and the second passage, and the recessed section has a shape in which the area of ​​an opening formed between the valve body and the bridge changes in two stages or gradations.

[0011] According to the invention, the recessed section comprises a first region in which the area of ​​the opening between the valve body and the bridge gradually increases, a second region connected to the first region in which the area of ​​the opening between the valve body and the bridge remains constant, a third region connected to the second region in which the area of ​​the opening between the valve body and the bridge gradually increases, and a fourth region connected to the third region in which the area of ​​the opening between the valve body and the bridge remains constant. A distance from a surface in the first region and a surface in the second region to the valve body is defined as the first distance, and a distance from a surface in the third region and a surface in the fourth region to the valve body is defined as the second distance, which is larger, respectively, than the first distance.is longer than the first distance. The first and third areas have a semicircular shape in a top view, with one dimension of the second and fourth areas being the same in a lateral direction. [Effect]

[0012] Because the recessed section formed on the bridge that blocks communication between the retraction-side actuator port and the second passage in the valve spool has a shape in which the area of ​​the opening formed between the valve body and the bridge changes in two stages, the invention allows the lifting mast to be stabilized, even if the reach truck is abruptly stopped during an extension operation, due to the function of the recessed section area with a small opening area. Furthermore, due to the function of the recessed section area with a large opening area, the lifting mast can be moved at high speed, and the load on the hydraulic oil supply pump can be reduced, thereby lowering power consumption.

[0013] According to the invention, the first, second, third and fourth areas can be easily processed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic view of a reach truck 10 to which a control valve 20 according to the present invention is applied. Fig. Figure 2 is a sectional view of the control valve 20 according to the present invention. Fig. Figure 3 is a sectional view of the control valve 20 according to the present invention. Fig. Figure 4 is a sectional view of the control valve 20 according to the present invention. Fig. Figure 5 is a top view showing a relationship between a valve body 40 and a recess section 41 formed on a web 31 in a main slide valve 30. Fig. Figure 6 is a vertical sectional view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30, the relationship being shown as a reference example. Fig. Figure 7 is a diagram showing a relationship between a position of the main slide 30 and an area of ​​an opening formed by recess sections 41, 42, 43, 44, 45, 46 and the like between the valve body 40 and the webs 31, 32, 33, 34, and 35 when the main slide is arranged at the position. Fig. Figure 8 is an enlarged view of a part in Fig. 7, in which the area of ​​the opening between the valve body 40 and the bridge 31 is formed when hydraulic oil passes from an in-line actuator port A to a second passage T. Fig. Figure 9 is a top view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide. Fig. Figure 10 is a vertical sectional view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30. Fig. Figure 11 is a diagram showing a relationship between a position of the main slide 30 and an area of ​​an opening formed by the recess sections 41, 42, 43, 44, 45, 46 and the like between the valve body 40 and the webs 31, 32, 33, 34, and 35 when the main slide is arranged at the position. Fig. 12 is an enlarged view of a part in Fig. 11, in which the area of ​​the opening between the valve body 40 and the bridge 31 is formed when the hydraulic oil passes from the in-line actuator port A to the second passage T. DESCRIPTION OF THE EXECUTION FORMS

[0014] An embodiment of the present invention is described below with reference to the drawings. First, a configuration of a reach truck 10 is described, to which a control valve 20 according to the present invention is applied. Fig. Figure 1 is a schematic view of the reach truck 10 to which the control valve 20 is applied according to the present invention.

[0015] The reach truck 10 is a type of reach truck capable of moving a mast 12, which raises and lowers a fork 11 carrying a workpiece, in a forward-backward direction between a retracted state (where the mast is retracted) and an extended state (where the mast is extended forward). The reach truck 10 has a main body 13 with a front wheel 14 and a rear wheel 15, a steering mechanism 16, and a lever 17 for performing various operations. A hydraulic cylinder 18 is arranged on a lower part of the main body 13, which moves the mast 12, which raises and lowers the fork 11, in a forward-backward direction.

[0016] Next, a configuration of the control valve 20 according to the present invention will be described. Fig. Figure 2 is a sectional view of the control valve 20 according to the present invention. The drawing also shows a state in which a main valve 30 is arranged in a neutral position.

[0017] The control valve 20 is a control valve coupled to the hydraulic cylinder 18, which moves the lifting mast 12, raising and lowering the forks 11. The control valve 20 is a control valve that connects a first passage P, into which high-pressure hydraulic oil from a hydraulic pump is introduced, and a second passage T, which leads to a low-pressure area such as a hydraulic tank, optionally to an inward-facing actuator port A for pre-tensioning a piston 19 of the hydraulic cylinder 18 towards the side on which the lifting mast 12 is moved backward, and to an outward-facing actuator port B for pre-tensioning the piston 19 of the hydraulic cylinder 18 towards the side on which the lifting mast 12 is moved forward.

[0018] The control valve 20 has a main spool 30 in which a plurality of webs 31, 32, 33, 34 and 35 and a plurality of grooves 36, 37, 38 and 39 are alternately formed and which is oriented in relation to a valve body 40 in a Fig. 2 can move back and forth in the left-right direction shown. A right end section of the main slide 30 is connected to the one shown in Fig. 1. Lever 17 shown is connected.

[0019] A recessed section 41 (A → T) is formed on the web 31. This section is used when hydraulic oil flows from the retraction-side actuator port A to preload the piston 19 of the hydraulic cylinder 18 towards the side on which the lifting mast 12 is moved rearward, towards the second passage T, which leads to the low-pressure area, such as the hydraulic tank. The recessed section 41 is a cut-out area, also referred to as a notch. As the hydraulic oil flows from the retraction-side actuator port A towards the second passage T, a transition occurs from a state where the flow of hydraulic oil through the web 31 is prevented to a state where the flow of hydraulic oil through the groove 36 is permitted. This transition takes place as soon as the control valve 20 is actuated by the high-pressure hydraulic oil.Therefore, the flow of hydraulic oil through the recessed section 41 prevents the effect from taking place.

[0020] For similar reasons, a recessed section 42 (P → A) is formed on web 32, which is used when the hydraulic oil flows from the first passage P to the retraction-side actuator port A, and a recessed section 43 (P → T) is formed, which is used when the hydraulic oil flows from the first passage P to the second passage T. Additionally, a recessed section 44 (P → T) is formed on web 34, which is used when the hydraulic oil flows from the first passage P to the second passage T, and a recessed section 45 (P → T) is formed, which is used when the hydraulic oil flows from the first passage P to the extension-side actuator port B. Furthermore, a recessed section 46 (B → T) is formed on web 35, which is used when the hydraulic oil flows from the extension-side actuator port B to the second passage T.

[0021] Next, the operation of the control valve 20 according to the present invention will be described. Fig. 3 and Fig. Figure 4 shows sectional views of the control valve 20, which are used to carry out the operations of the control valve 20 according to the present invention. The drawings also schematically depict the control valve 20, a workpiece W, the fork 11, the lifting mast 12, and the hydraulic cylinder 18. Fig. 3 a state in which the main valve 30 is arranged in a left-hand position, and Fig. Figure 4 shows a state in which the main slide valve 30 is arranged in a right-hand position.

[0022] As in Fig. Figure 2 shows that in the state where the main valve 30 is in the neutral position, the retraction-side actuator port A for pre-tensioning the piston 19 of the hydraulic cylinder 18 towards the side on which the lifting mast 12 is moved rearward, and the extension-side actuator port B for pre-tensioning the piston 19 of the hydraulic cylinder 18 towards the side on which the lifting mast 12 is moved forward, are separated by the action of the plurality of webs 31, 32, 33, 34, and 35 in the main valve 30 from the first passage P, into which the high-pressure hydraulic oil from the hydraulic pump is introduced, and the second passage T, which leads to the low-pressure area such as the hydraulic tank. Therefore, the hydraulic oil is not pressurized to the hydraulic cylinder 18.

[0023] If an operator enters Fig. The lever 17 shown in Figure 1 is actuated from the state described above, thereby moving the main slide 30, which is coupled to the lever 17, in a direction to the left as shown in Figure 1. Fig. As shown in Figure 3, the recessed section 45 and the groove 39 function to form a path for the hydraulic oil from the first passage P, through which the high-pressure hydraulic oil is introduced, to the extension-side actuator port B. Additionally, the recessed section 41 functions to form a path for the hydraulic oil from the retraction-side actuator port A to the second passage T, which leads into the low-pressure area, such as the hydraulic tank. As indicated by an arrow in Fig. As shown in Figure 3, the hydraulic oil flows, and the piston 19 of the hydraulic cylinder 18 moves towards the in Fig. 3 shown left side, and the lifting mast 12, which raises and lowers the fork 11, comes into the extended state in which the lifting mast is moved forward from one side of the main body 13.

[0024] If, on the other hand, the operator in Fig. 1 lever 17 shown from the one in Fig. 2 the depicted state is actuated and thereby the main slide 30 coupled to the lever 17 is moved towards a right side as in Fig. As shown in Figure 4, the recessed section 42 and the groove 36 function to form a path for the hydraulic oil from the first passage P, into which high-pressure hydraulic oil is introduced, to the retraction-side actuator port A. Furthermore, the recessed section 46 and the groove 39 function to form a path for the hydraulic oil from the extension-side actuator port B to the second passage T, which leads into the low-pressure area, such as the hydraulic tank. Consequently, the hydraulic oil flows as if through a Fig. As indicated by the arrow shown in section 4, the piston 19 of the hydraulic cylinder 18 moves in the direction shown in Fig. 4 right side shown, and the lifting mast 12, which raises and lowers the fork 11, comes into the retracted state, in which the lifting mast is moved towards the side of the main body 13.

[0025] With control valve 20, when the operator in Fig. When the lever 17 shown in Figure 1 is actuated in a state where the fork 11 carries the workpiece W, and the lifting mast 12, which raises and lowers the fork 11, is thereby extended, in which the lifting mast is moved forward from the side of the main body 13, the reach truck 10 is sometimes abruptly stopped. In these cases, a force is generated that causes the lifting mast 12 to separate or detach from the main body 13 and move in one direction of motion of a vehicle body, due to the inertial force of the workpiece W or the inertial force of the fork 11 and the lifting mast 12. Since the force is transmitted to the hydraulic cylinder 18, the pressure of the hydraulic oil in the hydraulic cylinder 18 decreases, and the force of the hydraulic cylinder 18 to fix or restrict a position of the lifting mast 12 in the forward-backward direction becomes unstable.Accordingly, the lifting mast 12, the fork 11 and the workpiece W, which are carried by the lifting mast, enter an unstable state.

[0026] The above situation will be described in more detail. Fig. Figure 5 is a top view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30, the relationship being shown as a reference example. Fig. Figure 6 is a vertical sectional view showing the relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30, with the relationship shown as a reference example. Fig. Figure 7 is a diagram showing a relationship between a position of the main slide 30 and an area of ​​an opening formed by the recess sections 41, 42, 43, 44, 45, 46 and the like between the valve body 40 and the webs 31, 32, 33, 34, and 35 when the main slide is arranged at the position. Fig. Figure 8 is an enlarged view of a part in Fig. 7, where the area of ​​the opening through which the Fig. 5 and Fig. The recess section 41 shown in Figure 6 is formed between the valve body 40 and the web 31 when hydraulic oil passes from the inlet-side actuator port A to the second passage T. Furthermore, the Fig. 7 and Fig. 8 the horizontal axis represents a movement distance or a movement path of the main slide 30, and the vertical axis represents the area of ​​the opening (in square millimeters).

[0027] For example, the dotted line in Fig. As illustrated in Figure 8, in a case where the area of ​​the opening formed by the recess section 41 between the valve body 40 and the web 31 during the passage of hydraulic oil from the retraction-side actuator port A to the second passage T is defined as large, the lifting mast 12, the forks 11, and the workpiece W supported by the lifting mast enter an unstable state when the lifting mast 12 is extended and the reach truck 10 is abruptly stopped. In contrast, as shown by the hatched part in Fig. As shown in Figure 8, in a case where the area of ​​the opening, which is set to be small by the recess section 41 between the valve body 40 and the web 31 when the hydraulic oil passes from the in-line actuator port A to the second passage T, an instability of the lifting mast 12 is reduced.

[0028] However, in a case where the area of ​​the opening, which is set to be small by the recess section 41 between the valve body 40 and the web 31 when the hydraulic oil passes from the retraction-side actuator port A to the second passage T, the flow rate of the hydraulic oil passing through a portion of the opening area decreases, and therefore a problem arises in that the forward movement speed of the fork 11 decreases in a case where an extension operation is performed.

[0029] Furthermore, in a case where the area of ​​the opening, which is set to a small size by the recessed section 41 between the valve body 40 and the web 31 during the passage of the hydraulic oil from the retraction-side actuator port A to the second passage T, the supply pressure of the hydraulic oil with respect to the hydraulic cylinder 18 increases when an extension movement is performed by the lever 17, and the current consumption for controlling the hydraulic pump that supplies the hydraulic oil increases. This creates the problem that a battery is quickly discharged.

[0030] Therefore, in the control valve 20 according to the present invention, the recessed section 41 is formed on the web 31 in the main slide 30, which blocks the communication of the inlet-side actuator port A with the second passage T, and the recessed section 41 is made to have a shape in which the area of ​​the opening formed between the valve body 40 and the web 31 changes in two stages, thereby solving the above problem.

[0031] Fig. Figure 9 is a top view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30 in the control valve 20 according to the present invention. Fig. Figure 10 is a vertical sectional view showing a relationship between the valve body 40 and the recess section 41 formed on the web 31 in the main slide 30 of the control valve 20 according to the present invention. Fig. Figure 11 is a diagram showing a relationship between a position of the main slide 30 and the area of ​​the opening formed by the recess section 41, 42, 43, 44, 45, 46 and the like between the valve body 40 and the webs 31, 32, 33, 34 and 35 when the main slide is arranged at the position. Fig. 12 is an enlarged view of a part in Fig. 11, in which the area of ​​the opening is increased by the in the Fig. 9 and Fig. The recess section 41 shown in Figure 10 is formed between the valve body 40 and the web 31 as the hydraulic oil passes from the inlet-side actuator port A to the second passage T. Furthermore, the Fig. 11 and Fig. 12 the horizontal axis represents a movement distance or a movement path of the main slide 30, and the vertical axis represents an area of ​​the opening (in square millimeters).

[0032] As shown in the drawings, in the control valve 20 according to the present invention, the recess section 41 is formed on the web 31 in the main slide 30, which blocks communication between the inlet-side actuator port A and the second passage T, and the recess section 41 is formed from a first recess section 41a and a second recess section 41b, and thereby has a shape in which a distance between the valve body 40 and a surface of the recess section 41 changes in two stages.

[0033] Specifically, the first recess section 41a of the recess section 41 is formed from a first area, which in a plan view has a semicircular shape and in which the area of ​​an opening between the valve body 40 and the web 31 gradually increases, and a second area, which is connected to the first area and in which the area of ​​an opening between the valve body 40 and the web 31 is constant, and the second recess section 41b of the recess section 41 is formed from a third area, which in a plan view has a semicircular shape and in which the area of ​​an opening between the valve body 40 and the web 31 gradually increases, and a fourth area, which is connected to the third area and in which the area of ​​an opening between the valve body 40 and the web 31 is constant.Furthermore, a distance from a surface in the first area and a surface in the second area to the valve body 40 is defined as a first distance, and a distance from a surface in the third area and a surface in the fourth area to the valve body 40 is defined as a second distance, which is longer than the first distance.

[0034] By applying the above design, the first recessed section 41a is used to connect the retraction-side actuator port A with the second passage T during the normal extension process. This makes it possible to reduce the area of ​​the opening formed between the valve body 40 and the web 31 as the hydraulic oil flows from the retraction-side actuator port A to the second passage T. Consequently, it is possible to control the flow rate of the hydraulic oil flowing from the retraction-side actuator port A to the second passage T, and it is possible to prevent instability of the mast 12 even if the reach truck 10 is abruptly stopped when the mast 12 is in the extended position.

[0035] If, however, the second recessed section 41b is used to connect the retraction-side actuator port A to the second passage T during normal operation, it is possible to increase the area of ​​the opening between the valve body 40 and the web 31 as the hydraulic oil flows from the retraction-side actuator port A to the second passage T. Consequently, in the case where the extension operation is carried out, the occurrence of a problem of a decrease in the forward movement speed of the fork 11 can be prevented.

[0036] Because the area of ​​the opening formed by the recessed section 41 between the valve body 40 and the web 31 as the hydraulic oil passes from the retraction-side actuator port A to the second passage T can be set to a large size, and because the supply pressure of the hydraulic oil with respect to the hydraulic cylinder 18 does not increase when the extension operation is carried out by the lever 17, the current consumption for controlling the hydraulic pump that supplies the hydraulic oil also does not increase. Therefore, battery consumption can be reduced.

[0037] In the embodiment described above, the first recess section 41a of the recess section 41 is formed from the first region, which has a semicircular shape in a top view and in which the area between the valve body 40 and the web 31 gradually increases, and the second region, which is connected to the first region and in which the area of ​​the opening between the valve body 40 and the web 31 is constant, and the second recess section 41b of the recess section 41 is formed from the third region, which has a semicircular shape in a top view and in which the area of ​​the opening between the valve body 40 and the web 31 gradually increases, and the fourth region, which is connected to the third region and in which the area of ​​the opening between the valve body 40 and the web 31 is constant.By applying the above shape, it is possible to form the first recess section 41a and the second recess section 41b in two stages by milling using an end-hole milling cutter or end-hole milling cutter. Therefore, it is possible to machine recess section 41 in a simple and cost-effective manner.

[0038] Furthermore, in the embodiment described above, the recess section 41 is formed on the web 31 in the valve slide 30, which blocks communication between the inlet-side actuator port A and the second passage T, and the recess section 41 has a shape in which the distance between the valve body 40 and the surface of the recess section 41 changes in two stages. However, the recess section 41 can be formed by changing a dimension of the recess section 41 in a width direction to a shape in which the area of ​​the opening formed between the valve body 40 and the web 31 changes in two stages. [List of reference symbols] 10 reach trucks 11 Fork 12 lifting mast 18 hydraulic cylinders 19 pistons 30 main valves 31 Bridge 40 valve bodies 41 Exclusion section 41a first exemption section 41b second exemption section A single-sided actuator connection B exit-side actuator connection P first passage T second passage

Claims

[1] Control valve (20) which is coupled to a hydraulic cylinder (18) for moving a lifting mast (12) forwards and backwards, wherein the lifting mast (12) serves to raise and lower a fork (11), wherein the control valve (20) moves a valve slide (30) in relation to a valve body (40) and thereby selectively connects a first passage (P) and a second passage (T) with an extension-side actuator port (B) and a retract-side actuator port (A), where high-pressure hydraulic oil is introduced through the first passage (P), and the second passage (T) leads into a low-pressure area, the extension-side actuator connection (B) serves to pre-tension a piston of the hydraulic cylinder (18) in the direction of a side on which the lifting mast (12) is moved forward, and the inward-facing actuator connection (A) serves to pre-tension the piston of the hydraulic cylinder (18) towards a side on which the lifting mast (12) is moved backwards, and wherein a recessed section (41) is formed on a web (31) in the valve slide (30), which blocks communication between the inlet-side actuator connection (A) and the second passage (T), and the recess section (41) has a shape in which the surface of an opening formed between the valve body (40) and the bridge (31) changes in two stages, wherein the exclusion section (41) has a first area, a second area, a third area and a fourth area, wherein in the first area the area of ​​the opening between the valve body (40) and the bridge (31) gradually increases, in the second area, which is connected to the first area, the area of ​​the opening between the valve body (40) and the bridge (31) is constant, in the third area, which is connected to the second area, the area of ​​the opening between the valve body (40) and the bridge (31) gradually increases, and in the fourth area, which is connected to the third area, the area of ​​the opening between the valve body (40) and the bridge (31) is constant, wherein a distance from a surface in the first region and a surface in the second region to the valve body (40) is defined as the first distance, and a distance from a surface in the third area and a surface in the fourth area to the valve body (40) is defined as the second distance, which is greater than the first distance, and wherein the first area and the third area have a semicircular shape in a top view, and where one dimension of the second area and the fourth area is the same in a lateral direction.

Images