Hydraulic actuator for a locking device of a telescopic boom, locking device, telescopic boom, mobile crane, and method for adjusting a telescopic boom

Abstract

To provide a hydraulic actuator for a locking device of a telescopic boom.SOLUTION: A hydraulic actuator (32) for a mobile crane (1), in particular, for a locking device (30) of a telescoping device (22) has: a double cylinder (34) with a first cylinder chamber (124) and a second cylinder chamber (128) oriented in an opposite direction to the first cylinder chamber; a first piston rod (102) for the first cylinder chamber (124), and a second piston rod (108) for the second cylinder chamber (128); a first restoring spring (100) for restoring the first piston rod (102) to its main position and a second restoring spring (101) for restoring the second piston rod (108) to its main position. The main position of the first piston rod (102) is its pushed-in position, and the main position of the second piston rod (108) is its extended position.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a hydraulic actuator for a locking device of a telescopic boom, in particular for a mobile crane. The present invention also relates to such a locking device. The present invention also relates to such a telescopic boom. The present invention also relates to a mobile crane equipped with such a telescopic boom. The present invention also relates to a method for adjusting such a telescopic boom. [Background technology]

[0002] A telescopic boom usually refers to a (mobile) crane assembly whose length is adjustable and which can usually be swiveled about a vertical and / or horizontal axis. The assembly is therefore usually used for lifting loads, particularly for transport. Such a telescopic boom is conventionally formed by a plurality of (i.e., at least two) boom elements displaceably arranged relative to one another. In this case, the boom elements are locked in their respective set positions relative to one another in at least one extended set position, usually also in a retracted set position. Therefore, no actuation force is required to maintain this set position. To lock the boom elements relative to one another, a "locking bolt" is conventionally form-lockedly engaged in both boom elements in a direction transverse to the longitudinal extension of the two boom elements. The locking bolt is usually movably arranged inside the two boom elements.

[0003] To adjust the length of the boom elements relative to one another, a telescoping boom typically includes a hydraulic cylinder located inside both or all of the boom elements. This hydraulic cylinder positively couples with the corresponding boom element to extend or retract it, and a locking device located on the hydraulic cylinder unlocks a locking bolt (or two locking bolts typically located on opposite longitudinal sides of the boom element), allowing each boom element to move relative to the surrounding boom elements. The hydraulic cylinder then moves longitudinally, thereby driving the moving boom element.

[0004] For a positive connection with the respective boom element, the hydraulic cylinder usually has a laterally displaceable drive bolt, which remains in a corresponding receiving part of the respective boom element during extension and retraction. Preferably, the drive bolt is then arranged in a section of the hydraulic cylinder in which a locking device for locking or unlocking the lock bolt is also arranged. This section of the hydraulic cylinder is also called the "lock head."

[0005] The drive bolts or locking devices are usually hydraulically actuated. The locking devices usually have a drive body arranged laterally displaceable relative to the hydraulic cylinder. This drive body engages with the respective locking bolt at a predetermined coupling position of the hydraulic cylinder to the telescopic boom element, thereby connecting them in a force-transmitting manner. As a result, the locking head of the hydraulic cylinder requires an actuator, in particular a hydraulic actuator for the drive bolt and the drive body, for locking or unlocking the locking bolt. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to improve the locking and unlocking of boom elements of a telescoping boom. [Means for solving the problem]

[0007] This problem is solved according to the invention by a hydraulic actuator having the features of claim 1. Furthermore, this problem is solved according to the invention by a locking device having the features of claim 7. Furthermore, this problem is solved according to the invention by a telescopic boom having the features of claim 8 and a mobile crane having the features of claim 9. Furthermore, this problem is solved according to the invention by a method having the features of claim 10. Advantageous, partly inventive, embodiments of the invention and further developments of the invention are set out in the dependent claims and the following description.

[0008] A hydraulic actuator (abbreviated as "actuator") according to the present invention is configured and provided for use with a mobile crane, in particular as part of a locking device for a telescoping gear of a mobile crane. To this end, the actuator comprises a double cylinder having a first cylinder chamber and a second cylinder chamber arranged opposite the first cylinder chamber. Correspondingly, the actuator comprises a first piston rod for the first cylinder chamber and a second piston rod for the second cylinder chamber. As is typical for hydraulic cylinders, these piston rods are displaceably mounted within the cylinder, specifically within the corresponding cylinder chamber. The actuator also comprises a first return spring for returning the first piston rod to its home position and a second return spring for returning the second piston rod to its home position. The home position of the first piston rod is located in its retracted position, and the home position of the second piston rod is located in its extended position.

[0009] Thus, the double cylinder preferably has a common (i.e., a common, generic for the double cylinder) basic position (also called the "neutral adjustment position") with the first piston rod retracted and the second piston rod simultaneously extended. This allows the actuator to be moved between a first operating position in which both piston rods are extended and a second operating position in which both piston rods are retracted, with only one of the two cylinder chambers actively pressurized. The common basic position is advantageously an intermediate position in terms of the length of the double cylinder. This facilitates positioning movements that require displacing the actuator in two opposite directions from the neutral adjustment position. This is particularly the case for locking devices (often called "lock heads") for telescopic cylinders used as telescopic devices for mobile cranes. Here, the telescopic cylinder is typically "bolted" to a boom element (also called a "extension boom section") slidably mounted on another boom element, in order to drive the boom element, in particular by a so-called drive bolt. The locking bolt is for locking to the outer boom element but must be released ("unlocked" or "unbolted") for adjustment (i.e., extension / retraction). By means of the actuator described here and below, the adjustment elements of the locking device, in particular the adjustment link, which acts on both the locking bolt and the drive bolt, can advantageously be adjusted. In this case, no additional actuation, such as a second cylinder, is required. The actuator according to the invention thereby enables a compact and inexpensive construction of the telescoping device of a crane element, in particular a mobile crane. Compared to a conventional double-acting cylinder, the double cylinder of the actuator according to the invention allows the respective home positions of the two piston rods, and therefore also the common home position, to be set relatively easily, in particular because both piston rods can be adjusted relative to the corresponding end stops.

[0010] Preferably, the actuator comprises a controller (also called a control unit or control device) configured to allocate hydraulic pressure to the first and second cylinder chambers, in particular independently of each other and preferably at different times, during a given movement of the telescopic boom of the mobile crane. In particular, applying hydraulic pressure to one of the two cylinder chambers involves depressurizing or de-pressurizing the other cylinder chamber. For this purpose, the controller is technically connected to a control valve of the hydraulic system.

[0011] In particular, the hydraulic system's piping system, which preferably includes at least a control valve, is part of the actuator. In the preferred case where the telescopic device used to apply the force required to extend or retract each extrusion boom section is formed by a hydraulic cylinder (particularly the aforementioned "telescopic cylinder", also called "tele-cylinder" for short), the hydraulic system is preferably coupled to the hydraulic volume of the tele-cylinder in a given operating state. This allows hydraulic pressure to be obtained from the tele-cylinder to drive the double cylinder. This advantageously eliminates the need for a separate supply line to the actuator.

[0012] In a preferred embodiment, the first return spring is arranged in a spring cage fixedly connected to the double cylinder. Furthermore, the first return spring is supported by the spring cage against a spring seat arranged on the push-in side of the first piston rod. This provides support for the first return spring in the push-in direction of the first piston rod, independent of the mounting state of the double cylinder. The spring cage is formed, in particular, by a further spring seat (in particular arranged on the push-in side of the first piston rod) and a linkage rod connecting the spring seat to the double cylinder. Preferably, the linkage rods are a number of threaded rods, preferably three. Each of the threaded rods forms a support column by means of which the spring seats of the spring cage can be adjusted relative to the double cylinder, in particular to adapt the mounting state and / or the spring characteristic curve of the first return spring. Alternatively, the linkage rods are configured to hold the spring seats in a fixed position, for example by welding them to the corresponding linkage rods.

[0013] In contrast, the second return spring is preferably arranged, in particular tension-fixed, between the double cylinder (optionally a spring seat fixedly connected to the double cylinder) and a spring seat arranged on the push side of the second return spring.

[0014] In a preferred embodiment, the double cylinder and two piston rods are configured such that the first piston rod is hydraulically moved in the push direction and the second piston rod is hydraulically moved in the push direction. In particular, a hydraulic inlet (or connection port) for hydraulic fluid to the second cylinder chamber is arranged near or at the longitudinal end of the push side of the second cylinder chamber. This ensures that hydraulic fluid is always present on the piston face on the push side of the piston supported by the second piston rod. Correspondingly, a hydraulic inlet for the first cylinder chamber is arranged at the longitudinal end of the push side of the first cylinder chamber.

[0015] In a further preferred embodiment, the first piston rod carries a plunger piston (also called "plunger") as the assigned first piston (projecting radially beyond the first piston rod). The plunger piston has a (longitudinal) groove that allows hydraulic fluid to flow around the plunger piston. This, however, reduces the effective area of ​​the first piston. Nevertheless, such a plunger piston is more mechanically efficient than a typical piston. Furthermore, the plunger piston serves as an end stop and thereby also as a mechanical fixation device for the first piston rod in the extrusion direction.

[0016] In a preferred embodiment, the second chamber is connected to an exhaust valve inside the piston, in particular to the surroundings, so that when adjusting the piston of the second piston rod, under- or over-pressure in the fluid-free part of the second chamber can be prevented, which would reduce efficiency.

[0017] As mentioned above, in a preferred embodiment, the first and second cylinder chambers are hydraulically pressurizable independently of each other, in particular the hydraulic pressure being "allocated" to the respective cylinder chambers by the control device, in particular by corresponding switching of the control valves.

[0018] As described above, a locking device according to the present invention is provided and configured for use with a telescopic boom, particularly a telescopic boom of a mobile crane. The locking device includes the hydraulic actuator described above for generating an actuating force. The locking device further includes at least one driver configured to reversibly couple with an assigned locking bolt secured to an extension boom section of the telescopic boom during telescopic operation of the telescopic boom, and configured to move between at least one locked position and a released position under the action of an actuating force for adjusting the locking bolt. The locking device further includes at least one drive bolt configured to reversibly move under the action of an actuating force between a drive position in which it captures the inner extension boom section and an idle position in which it does not capture any extension boom section. The locking device further includes an adjustment link (preferably utilizing its own movement driven by the actuating force) configured for cooperative movement of the locking bolt and the drive bolt (particularly by the transmission of the actuating force thereto). The (preferably only) plane of movement of the adjustment link is perpendicular to the telescopic boom extension direction in a predetermined assembled state.

[0019] The adjustment link is arranged so that its plane of movement is perpendicular to the extension / retraction direction, which simplifies the control, in particular the transmission of the actuation to the driver and the drive bolt by only one element, namely the adjustment link.

[0020] The telescopic boom according to the present invention is used in a mobile crane and comprises a predetermined number of boom elements movably attached to one another, a telescopic drive device (particularly the above-mentioned telescopic device), and the above-mentioned locking device.

[0021] A mobile crane according to the present invention is provided with the telescopic boom described above.

[0022] Therefore, the locking device, telescopic boom and mobile crane according to the present invention comprise an actuator according to the present invention, and thereby share the advantages described in the context of that actuator.

[0023] The method according to the invention is used to adjust the telescopic boom. According to this method, in order to lock one of the inner boom elements (or: extrusion boom sections) to the next outer boom element (optionally the outermost boom element also referred to as the "base element"), the first cylinder chamber is hydraulically pressurized and the second cylinder chamber (128) is depressurized. The drive bolt is then decoupled from the inner boom element (in particular based on the movement of the adjustment link). In order to unlock the inner extrusion boom section from the next outer extrusion boom section (or base element), the first cylinder chamber is depressurized and the second cylinder chamber is hydraulically pressurized. The lock bolt is then decoupled from the next outer boom element (in particular based on the movement of the adjustment link limited thereby) and the drive bolt is connected to the inner boom element.

[0024] Preferably, the controller is at least at its core a microcontroller with a processor and a data memory. The functions for controlling the locking device, in particular the actuators, are implemented in the microcontroller in a program-technical manner in the form of operating software (firmware). Alternatively, however, the controller can also be formed by non-programmable electronic components, such as an ASIC, in which the control functions are implemented by circuit-technical means. Furthermore, purely electrical control is also optionally provided, in that (preferably existing) hydraulic valves can be controlled directly (i.e., without intervening logic) by means of (in particular manually operable) switches integrated into the corresponding control wiring. This preferably serves as an emergency control in the event of a failure of the electronic controller, provided that the hydraulic supply is available.

[0025] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic side view of a mobile crane with a telescoping boom and telescoping device. FIG. [Figure 2] FIG. 1 is a partial cross-sectional perspective view of a telescopic boom with a part of a telescopic device and a locking device. [Figure 3] FIG. 2 is a schematic side view showing the locking device individually. [Figure 4] FIG. 2 is a schematic perspective view showing a locking device individually. [Figure 5] 1A-1C are schematic front views showing the locking device in two different states; [Figure 6] FIG. 10 is a schematic front view showing another state of the locking device. [Figure 7] FIG. 2 is a schematic side view of a hydraulic cylinder of the locking device. [Figure 8] 2 is a schematic longitudinal cross-sectional view of a hydraulic cylinder of a locking device. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0027] In all the figures, parts that correspond to one another are always provided with the same reference signs.

[0028] FIG. 1 shows a schematic representation of a crane, specifically a mobile crane 1. The mobile crane 1 comprises an undercarriage 2 with a chassis having a number of axles carrying wheels 4 and a cockpit 6. The mobile crane 1 further comprises an upper rotating body 8 hinged to the undercarriage 2 for rotation about a vertical axis 10. The mobile crane 1 further comprises a crane boom (also called a "telescopic boom", hereinafter abbreviated as "boom 12") which forms part of the upper rotating body 8 and is hinged to a mounting base of the upper rotating body 8 so as to be rotatable ("telescopic", i.e., so that its tilt can be adjusted) about a hoisting axis 14. The boom 12 is telescopic and, for this purpose, has a base element 16 in which several further boom elements (also: "extension boom sections 18"), each having a smaller cross section, are accommodated so as to be displaceable along a longitudinal axis 20 of the crane boom 12. To extend and retract the boom 12, the boom has a telescopic device formed in this embodiment by a hydraulically operated telescopic cylinder (abbreviated as "telescopic cylinder (tele-cylinder) 22").

[0029] The telescopic cylinder 22 is locked to the base region of the base element 16 by its piston rod 24. The telescopic cylinder 22 further carries a locking device 30 arranged on the rod end of its cylinder 28. The locking device 30 serves to catch one of the extrusion boom sections 18 during extension and retraction of the boom 12 and to lock or secure this extrusion boom section 18 in the target position relative to the next outer extrusion boom section 18 or, as the case may be, to the base element 16.

[0030] As can be seen from FIG. 2 , the locking device 30 includes a (hydraulic) actuator 32, which in this embodiment includes a double-acting hydraulic cylinder, specifically a double cylinder 34 in the form of a modified plunger cylinder (also referred to as a "plunger cylinder"). Furthermore, the locking device 30 includes two drivers 36 arranged oppositely along a movement axis 35 perpendicular to the longitudinal axis 20, and two similarly arranged drive bolts 38 (see also FIGS. 4 and 6 ; for clarity, only the drive bolt on the left side is always labeled in the drawings). To transmit the actuation force generated by the actuator 32 to the drivers 36 and the drive bolts 38 and thus adjust them, the locking device 30 also includes an adjustment link 40. The adjustment link 40 is arranged so that its plane of movement is radial to the longitudinal axis 20 (corresponding to the extension / retraction direction of the boom 12). Specifically, the movement direction of the adjustment link 40 is in the plane of the boom 12 (i.e., from bottom to top in FIGS. 5 and 6 , or vice versa).

[0031] In addition to the plunger cylinder 34, the actuator 32 has a lever movement mechanism 42. The lever movement mechanism 42 serves to convert the linear movement generated by the plunger cylinder 34 into the adjustment link 40 (see FIG. 3) by rotation.

[0032] The adjusting link 40 is formed by a substantially H-shaped or Ω-shaped plate for leaving a space 44 free for the piston rod 24. This plate is provided with a first link groove 46 for each driver 36 and a second link groove 48 for each drive bolt 38. Thus, the adjusting link 40 has two link grooves: a first link groove 46 and a second link groove 48. The driver 36 and the drive bolt 38 are hinged by a respective link rod 49 in the respective link groove 46 or 48 for adjustment in a radial direction relative to the longitudinal axis 20, specifically in the direction of the assigned longitudinal side of the boom 12. Furthermore, the driver 36 or the drive bolt 38 is guided in a slide rail 50 or slide sleeve (not shown) along the respective axis of movement 35.

[0033] The drive bolts 38 are configured and provided for connecting the telescopic cylinder 22 to the extrusion boom section 18 to be adjusted during the telescopic movement. To this end, the drive bolts 38 are assigned to the locking devices 30. The drivers 36 are used to respectively adjust, under the action of an actuation force, the respective locking bolts 52 for locking (or: "bolting") the extrusion boom section 18 to the next outer extrusion boom section 18 or to the base element 16. The locking bolts 52 are assigned to the extrusion boom section 18 because, as is known, the extrusion boom section 18 must remain in its telescopic position after the telescopic movement. In other words, each extrusion boom section 18 has a pair of locking bolts 52.

[0034] Not only the driver 36, but also the adjusting link 40 is configured so that the driver 36 can be reversibly coupled to the respective locking bolt 52. To this end, each driver 36 is claw-shaped. Specifically, each driver 36 has a T-slot 54. Each locking bolt 52 has a T-head 56 at its inner end, which corresponds to the T-slot 54 (see FIGS. 4 and 6). To extend or retract the extrusion boom section 18, the telescopic cylinder 22 is first adjusted so that the locking device 30 is located in the "base area" of the corresponding extrusion boom section 18. There, the extrusion boom section 18 has a portion also referred to as a "bearing block 58." A sliding element 60 is arranged on the bearing block 58, particularly on the outer side, and the sliding element 60 slides inside the next outer extrusion boom section 18 or base element 16. Furthermore, the bearing block 58 has bolt fixing holes (not shown) for receiving the drive bolt 38 as well as the lock bolt 52 which is guided in a guide sleeve 62 (see Figures 4 and 5, only the left side is shown in Figure 5).

[0035] When the telescopic cylinder 22 with the locking device 30 "enters" the area of ​​the bearing block 58, the driver 36 with the T-slot 54 slides over the T-head 56 of the locking bolt 52, thereby capturing the T-head 56. In this state, the locking device 30 can adjust the locking bolt 52, i.e., release (also: "pull") the locking bolt 52, or push it outward along the movement axis 35 and lock the respective extrusion boom section 18. The locking bolt 52 is arranged in the bearing block 58 so that it is pushed into a locking position 64 under the action of an adjusting spring (not shown in detail). In this case, in the locking position 64, the locking bolt 52 extends outward beyond the bearing block 58 (see FIG. 6) and can thereby engage with a corresponding bolt fixing hole (not shown) in the next outer extrusion boom section 18 or base element 16.

[0036] As shown in Figures 4-6, the adjustment link 40 is adjustable between three adjustment positions. An upwardly pulled end adjustment position (also referred to as the telescopic adjustment position 66) is shown in Figure 5. A downwardly pushed end adjustment position (also referred to as the fixed adjustment position 68) is shown in Figure 6. A neutral adjustment position 70, located between the telescopic adjustment position 66 and the fixed adjustment position 68, is shown in Figure 4.

[0037] The second link groove 48 has two straight curved segments that are angled relative to one another, thereby forming a single bend. The first link groove 46 has three straight curved segments that are angled relative to one another, thereby forming a double bend. The curved segments at each end of the link groove 46 or 48 are referred to as the fixed portion 72 and the retracted portion 74. The third, "middle" curved segment of the first link groove 46 is referred to as the neutral portion 76. The fixed portion 72 is aligned parallel to the direction of movement of the adjustment link 40, while the retracted portion 74 is angled inward relative to the extension direction of the driver 36 or drive bolt 38. As can be seen in FIGS. 5 and 6, the fixed portion 72 and the retracted portion 74 of the first link groove 46 and the second link groove 48 are aligned oppositely relative to the direction of movement of the adjustment link 40.

[0038] This results in opposite movements or adjustments of the drive bolt 38 and the lock bolt 52. In the telescopic adjustment position 66, the lock bolt 52 is retracted to a release position 78 in which it does not engage with the outer push-out boom section 18 or the base element 16, i.e., the adjustment of the inner push-out boom section 18 is released. Meanwhile, the drive bolt 38 is extended to a so-called drive position 80 in which it engages with the bearing block 58.

[0039] In contrast, in the fixed adjustment position 68 of the adjusting link 40 (see FIG. 6), the locking bolt 52 is in its locked position 64 and the drive bolt 38 is retracted to an idle position 82. This allows the telescopic cylinder 22 to move without driving the extrusion boom section 18, while the locking bolt 52 is extended to lock the extrusion boom section 18 (so-called "idling").

[0040] While the driver 36 moves inward or outward along the assigned retraction portion 74, the drive bolt 38 remains in its locked, i.e., driven, position 80 (and vice versa) because the fixed portion 72 is positioned parallel to the direction of movement of the adjustment link 40.

[0041] In the neutral adjustment position 70, the link rod 49 of the driver 36 is located in the region of the neutral section 76. The neutral section 76 is flatter, i.e., it is angled at a smaller angle relative to the extension direction, i.e., the axis of movement 35, than the retracted section 74. This reduces friction when manually moving the locking bolt 52 from the outside toward the release position 78. As a result, the neutral section 76 allows for emergency unlocking of the locking bolt 52. Furthermore, due to the position and width of the first link groove 46 in the region of the neutral section 76, the link rod 49 has a relatively large play along the axis of movement 35 of the driver 36. This simplifies tolerance compensation in the region of the bearing block 58 and manual insertion of the locking bolt 52.

[0042] To enable the adjustment position of the adjusting link 40 to be detected, the locking device 30 has a position encoder 90, which is arranged in the area of ​​the lever movement mechanism 42 and is configured to detect the rotational position. For this purpose, the position encoder 90 has two proximity switches 92 and an encoding plate 94 made of a metal plate with an opening as an encoding field. The position of the encoding plate 94 is thus detected by the proximity switches 92 depending on whether the encoding field or the metal plate wall faces the corresponding proximity switch 92. As is known, this implementation of the position encoder 90 is resistant to contamination by lubricating oil or hydraulic media and, due to the particularly selected large components, is also resistant to vibrations.

[0043] A proximity switch 96 is also assigned to the driver 36 so that the actual position of the driver 36 can be determined. The proximity switch 96 is used to detect whether the driver 36, and thus the locking bolt 52, is positioned in the locked position 64 and thus whether the extrusion boom section 18 is locked. This also allows a conclusion to be drawn as to whether the corresponding extrusion boom section 18 is positioned in a predetermined extension / retraction adjustment position. This is because the control device 98 controls the locking device 30 during extension / retraction of the extrusion boom section 18 so that the adjustment link 40 is positioned in the neutral adjustment position 70 when the outer extrusion boom section 18 or base element 16 enters the bolting area. This allows the driver 36 and the locking bolt 52 to already come into contact with the inside of the outer bolting area due to the play in the neutral section 76 and the outward spring load. As a result, the locking bolt 52 can "contact-check" the assigned bolting hole when it "passes over."

[0044] 3, 7 and 8, the plunger cylinder 34 is spring-loaded by a first return spring 100 and a second return spring 101 to return to its home position in the unpressurized state, thereby adjusting the adjustment link 40 to its neutral adjustment position 70. For this purpose, the first return spring 100 is connected to the first piston rod 102 and a "spring cage 104", thereby pushing the first piston rod 102 back into the cylinder 106. On the other hand, the second return spring 101 is arranged between the cylinder 106 and the second piston rod 108, thereby pulling the second piston rod 108 out of the cylinder 106 (to its assigned home position) in the unpressurized state.

[0045] The spring cage 104 has a spring seat 110 and a linkage rod consisting of a plurality of support posts 112, specifically three in this embodiment, which position the spring seat 110 relative to the cylinder 106. The first return spring 100 is arranged, specifically fixed in tension, between the spring seat 110 and a further spring seat 114 attached to the first piston rod 102.

[0046] The support post 112 is formed by a threaded rod that allows the length of the spring cage 104, and in particular the spring seat 110, to be adjusted relative to the cylinder 106, thereby adjusting the preload of the first return spring 100.

[0047] The second return spring 101 is disposed between a spring seat 116 on the side of the cylinder, i.e., connected to the cylinder 106, and another spring seat 118 attached to the second piston rod 108, and is specifically fixed in tension.

[0048] The first piston rod 102 supports a plunger piston 120 (which gives its name to the plunger cylinder 34) (see also FIG. 8) having a longitudinal groove 122, thereby providing a fluid connection between the front piston face and the rear piston ring face. The plunger piston 120 is disposed in a first cylinder chamber 124 of the cylinder 106, which is separated from a second cylinder chamber 128 by a partition wall 126. Regardless of which part of the first cylinder chamber 124 the first hydraulic inlet 130 leads to, the plunger piston 120 is always pushed against the first return spring 100 when pressure is applied to the first cylinder chamber 124.

[0049] A "normal", in particular substantially cylindrical, piston 132 is guided in the second cylinder chamber 128 and connected to the second piston rod 108. In this case, a second hydraulic inlet 134 assigned to the second cylinder chamber 128 is arranged on the outside, i.e., on the side of the piston 132 facing the second piston rod 108. As a result, the piston 132 is pressed into the cylinder 106 under pressure. In this connection, to avoid counterpressure due to the compressed air cushion, an exhaust valve 136 is connected to the second cylinder chamber 128 on the inside, in particular in the region of the partition wall 126.

[0050] In the absence of hydraulic pressure, the plunger piston 120 and the piston 132 are placed in the positions shown in FIGS. 7 and 8 by the two return springs, so that the plunger cylinder 34 has the neutral position described above.

[0051] Now, to adjust the adjusting link 40 to its fixed adjustment position 68, i.e., to push the locking bolt 52 outward to its locking position 64 or to hold it in this position, the first cylinder chamber 124 is hydraulically pressurized. This displaces (i.e., pushes) the plunger piston 120 by its assigned adjustment stroke 138. The lever movement mechanism 42 redirects this linear adjustment movement, so that the adjusting link 40 descends, i.e., displaces downwards (as seen in the images according to FIGS. 1 to 6). In so doing, the second cylinder chamber 128 remains unpressurized. The link rod 49 of the driver 36 slides along the fixed portion 72 of the link groove.

[0052] In contrast, to move the adjustment link 40 to the telescopic adjustment position 66, the first cylinder chamber 124 is first depressurized and the second cylinder chamber 128 is pressurized. This causes the plunger piston 120 to "retract" and the piston 132 to extend its adjustment stroke 140. This adjustment movement is then transmitted to the adjustment link 40 via the lever movement mechanism 42, lifting the adjustment link 40. This causes the driver 36 to retract, and the lock bolt 52 to similarly retract, resulting in the "release" or "bolt-unlock" of the lock bolt 52. Meanwhile, the drive bolt 38 is secured to the next outer extrusion boom section 18 or base element 16, i.e., is extruded.

[0053] Thus, the control device 98 is configured to apply hydraulic pressure essentially independently to the two cylinder chambers 124 and 128. Preferably, however, depressurization of one of the cylinder chambers 124 or 128 is performed in conjunction with pressurization of the other cylinder chamber 128 or 124.

[0054] It should be noted that the subject matter of the present invention is not limited to the examples described above, but rather further embodiments of the invention can be derived from the above description by those skilled in the art. [Explanation of symbols]

[0055] 1. Mobile crane 2 Undercarriage 4 wheels 6 Cockpit 8 Upper rotating body 10 vertical axis 12 Boom (telescopic boom) 14 Relief axis 16 Base element (boom element) 18 Extrusion boom section (boom element) 20 Longitudinal Axis 22 Telescopic device (telescopic cylinder) 24 Piston rod 28 cylinders 30 Locking device 32 Actuator 34 Double cylinder (plunger cylinder) 35 Moving axis 36 Driver 38 Drive bolt 40 Adjustment Link 42 Lever movement mechanism 44 void 46 Link groove 48 Link groove 49 Link rod 50 slide rail 52 Rock Bolt 54 T groove 56 T-head 58 Bearing Block 60 Slide Elements 62 Guide sleeve 64 Lock position 66 Telescopic adjustment position 68 Fixed adjustment position 70 Neutral adjustment position 72 Fixed part 74 Retraction section 76 Neutral section 78 Release position 80 Drive position 82 Idling position 90 Position Encoder 92 Proximity switch 94 Encode Plate 96 Proximity Switch 98 Control Device 100 First return spring 101 Second return spring 102 first piston rod 104 Spring cage 106 cylinders 108 Second piston rod 110 spring seat 112 Support column 114 Spring seat 116 Spring seat 118 Spring seat 120 Plunger Piston 122 longitudinal groove 124 First cylinder chamber 126 Partition Wall 128 Second cylinder chamber 130 First hydraulic inlet 132 Piston 134 Second hydraulic inlet 136 Exhaust valve 138 Adjustment stroke 140 Adjustment stroke

Claims

1. A hydraulic actuator (32) for a locking device (30) of an extension device (22) in a mobile crane (1), comprising: a double cylinder (34) having a first cylinder chamber (124) and a second cylinder chamber (128) disposed in an opposite direction to the first cylinder chamber; a first piston rod (102) for the first cylinder chamber (124) and a second piston rod (108) for the second cylinder chamber (128); a first return spring (100) for returning the first piston rod (102) to a home position, and a second return spring (101) for returning the second piston rod (108) to a home position; The home position of the first piston rod (102) is disposed in its pushed-in position, and the home position of the second piston rod (108) is disposed in its extended position.

2. The first return spring (100) is disposed in a spring cage (104) fixedly connected to the double cylinder (34); 2. The hydraulic actuator (32) of claim 1, wherein the first return spring (100) is supported by the spring cage (104) against a spring seat (114) disposed on a pushing side of the first piston rod (102).

3. 3. The hydraulic actuator (32) according to claim 2, wherein the double cylinder (34) and the two piston rods (102, 108) are configured so that the first piston rod (102) moves in a push-out direction by hydraulic pressure, and the second piston rod (108) moves in a push-in direction by hydraulic pressure.

4. The hydraulic actuator (32) of claim 3, wherein the first piston rod (102) supports a plunger piston (120).

5. The hydraulic actuator (32) according to claim 4, wherein the second cylinder chamber (128) is connected to an exhaust valve (136) inside the piston.

6. 6. The hydraulic actuator (32) of claim 5, wherein the first and second cylinder chambers (124, 128) are hydraulically pressurizable independently of one another.

7. A locking device (30) for a telescopic boom (12) of a mobile crane (1), comprising: a hydraulic actuator (32) according to any one of claims 1 to 6 for generating an actuation force; at least one driver (36), configured to reversibly couple to an assigned lock bolt (52) held on the extrusion boom section (18) of the telescopic boom (12) during telescopic operation of the telescopic boom (12), and configured to move between at least one lock position (64) and a release position (78) under the action of the actuation force for adjusting the lock bolt (52); at least one drive bolt (38) configured to reversibly move under the action of the actuation force between a drive position (80) in which it captures an inner push-out boom section (18) and an idle position (82) in which it does not capture any push-out boom section (18); and an adjusting link (40) configured for cooperative movement of the lock bolt (52) and the drive bolt (38), wherein the plane of movement of the adjusting link (40) is perpendicular to the direction of extension and retraction of the telescopic boom (12) in a predetermined assembled state.

8. a predetermined number of interdigitated and movably mounted boom elements (16, 18); an expansion device (22); A telescopic boom (12) for a mobile crane (1), comprising a locking device (30) according to claim 7.

9. A mobile crane (1) equipped with a telescopic boom (12) according to claim 8.

10. A method for operating a telescopic boom (12) according to claim 8, comprising the steps of: hydraulically pressurizing the first cylinder chamber (124) and depressurizing the second cylinder chamber (128) to lock one of the inner boom elements (18) to the next outer boom element (16, 18), and disengaging the drive bolt (38) from the inner boom element (18); A method of operating a telescoping boom (12) comprising depressurizing the first cylinder chamber (124) and hydraulically pressurizing the second cylinder chamber (128) to unlock the inner boom element (18) from the next outer boom element (16, 18), disengaging the lock bolt (52) from the next outer boom element (16, 18) and connecting the drive bolt (38) to the inner boom element (18).

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