HYDRAULIC ACTUATOR FOR A LOCKING DEVICE OF A TELESCOPIC BOOM, LOCKING DEVICE, TELESCOPIC BOOM, MOBILE CRANE, AND METHOD FOR ADJUSTING A TELESCOPIC BOOM

Abstract

A hydraulic actuator for a mobile crane, in particular for a locking device of a telescoping device. The hydraulic actuator has a double chamber cylinder with a first cylinder chamber and a second cylinder chamber oriented in an opposite direction to the first cylinder chamber, a first piston rod for the first cylinder chamber, and a second piston rod for the second cylinder chamber. A first restoring spring restores the first piston rod to its main position and a second restoring spring restores the second piston rod to its main position. The main position of the first piston rod is its pushed-in position and the main position of the second piston rod is its extended position.

Claims

1. A hydraulic actuator for a mobile crane, the hydraulic actuator comprising: a double chamber cylinder formed with a first cylinder chamber and a second cylinder chamber oriented opposite said first cylinder chamber; a first piston rod associated with said first cylinder chamber and a second piston rod associated with said second cylinder chamber; a first restoring spring configured for restoring said first piston rod to a main position thereof wherein said first piston rod is in a pushed-in position in said first cylinder chamber; and a second restoring spring configured for restoring said second piston rod into a main position thereof wherein said second piston rod is in an extended position.

2. The hydraulic actuator according to claim 1, configured for actuating a locking device of a telescoping device.

3. The hydraulic actuator according to claim 1, wherein said first restoring spring is disposed in a spring cage which is rigidly mounted to said double chamber cylinder, and wherein said first restoring spring is supported in said spring cage against a spring plate arranged on a push-in side of said first piston rod.

4. The hydraulic actuator according to claim 1, wherein said double chamber cylinder and said first and second piston rods are configured to cause said first piston rod to be moved by hydraulic pressure in an extension direction and to cause said second piston rod to be moved by hydraulic pressure in a push-in direction.

5. The hydraulic actuator according to claim 1, further comprising a plunger piston disposed on said first piston rod.

6. The hydraulic actuator according to claim 1, further comprising a venting valve connected to said second cylinder chamber on a piston inner side.

7. The hydraulic actuator according to claim 1, wherein said first and second cylinder chambers are chargeable with hydraulic pressure independently of one other.

8. A locking device for a telescopic boom, comprising: a hydraulic actuator for generating an actuating force, said hydraulic actuator including: a double chamber cylinder formed with a first cylinder chamber and a second cylinder chamber oriented opposite said first cylinder chamber; a first piston rod associated with said first cylinder chamber and a second piston rod associated with said second cylinder chamber; a first restoring spring configured for restoring said first piston rod to a main position thereof wherein said first piston rod is in a pushed-in position in said first cylinder chamber; and a second restoring spring configured for restoring said second piston rod into a main position thereof wherein said second piston rod is in an extended position; at least one driver configured to be reversibly coupled, during a telescoping movement of the telescopic boom, to a locking bolt that is secured at a boom extension segment of the telescopic boom, and to be moved by the actuating force for adjusting the locking bolt between a locking position and a release position; at least one driver bolt configured to be reversibly moved by the actuating force between a carry-along position, gripping an inner boom extension segment, and an empty running position in which no boom extension segment is gripped; and a slotted actuating link configured for a joint movement of the locking bolt and said driver bolt, said slotted actuating link, in an installation state as intended, having a movement plane oriented perpendicular to a telescoping direction of the telescopic boom.

9. The locking device according to claim 8, configured for a telescopic boom of a mobile crane.

10. A telescopic boom for a mobile crane, comprising: a plurality of boom segments mounted displaceably inside one another, a telescoping device, and the locking device according to claim 8.

11. A mobile crane, comprising a telescopic boom according to claim 10.

12. A method, comprising: providing a telescopic boom according to claim 10 and operating the telescopic boom by selectively: locking an inner boom segment of the boom segments to a next outer boom segment by charging the first cylinder chamber with hydraulic pressure and switching the second cylinder chamber to an unpressurized state, wherein the driver bolt is decoupled from the inner boom segment; and unlocking the inner boom segment from the next outer boom segment by switching the first cylinder chamber to an unpressurized state and charging the second cylinder chamber with hydraulic pressure, wherein the locking bolt is decoupled from the next outer boom segment and the driver bolt is coupled to the inner boom segment.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] FIG. 1 is a schematic side view of a mobile crane with a telescopic boom and a telescoping device;

[0040] FIG. 2 is a perspective partial sectional illustration of the telescopic boom with a part of the telescoping device and a locking device;

[0041] FIG. 3 is a schematic side view of the locking device separately;

[0042] FIG. 4 is a perspective view of the locking device separately;

[0043] FIGS. 5 and 6 are schematic frontal views showing the locking device in different states;

[0044] FIG. 7 is a schematic side view of a hydraulic cylinder of an actuator of the locking device; and

[0045] FIG. 8 is a longitudinal section of the hydraulic cylinder of the actuator of the locking device.

[0046] Parts corresponding to one another are provided with the same reference signs throughout the figures.

DETAILED DESCRIPTION OF THE INVENTION

[0047] Referring now to the figures of the drawing in detail and first, in particular, to FIG. 1 thereof, there is shown a simple schematic illustration of a crane, specifically a mobile crane 1. The latter comprises an undercarriage 2 which, in turn, has a chassis with a plurality of driving axles carrying wheels 4, and a cockpit 6. The mobile crane 1 also comprises a superstructure 8 which is rotatably coupled to the undercarriage 2 about a vertical axis 10. In addition, the mobile crane 1 comprises a crane boom (also: “telescopic boom”; “boom 12” for short below) which forms part of the superstructure 8 and which is coupled to a mounting of the superstructure 8 so as to be pivotable about a rocker axis 14 (“tiltably”, i.e., adjustably in terms of its inclination). The boom 12 is telescopic and, for this purpose, has a main segment 16 in which a plurality of further boom segments (also: “boom extension segments 18”), each reduced in size in cross section, are accommodated displaceably along a longitudinal axis 20 of the crane boom 12. For the telescoping of the boom 12, the latter has a telescoping device, formed in the present exemplary embodiment by a hydraulically operated telescoping cylinder (“telescope cylinder 22” for short).

[0048] The telescope cylinder 22 is arrested with its piston rod 24 in the base region of the main segment 16. The telescope cylinder 22 also bears a locking device 30 arranged at the rod-side end of its cylinder 28. Said locking device serves to grip one of the boom extension segments 18 during the telescoping of the boom 12 and to lock, i.e., arrest, said boom extension segment 18, in its target position, to the next outer boom extension segment 18 or optionally to the main segment 16.

[0049] As is apparent from FIG. 2, the locking device 30 has a (hydraulic) actuator 32 which, in the present exemplary embodiment, comprises a double-action hydraulic cylinder, specifically a double chamber cylinder in the form of a modified plunger cylinder 34 (also referred to as “plunger piston cylinder”). In addition, the locking device 30 has two diametrically opposite drivers 36, a movement axis 35 of which is oriented perpendicularly to the longitudinal axis 20, and two identically arranged driver bolts 38 (also see FIGS. 4 and 6; for the sake of clarity, only the left driver bolt in the drawing is ever labeled). For the transmission of the actuating force generated by the actuator 32 to the drivers 36 and the driver bolts 38 and therefore for the adjustment thereof, the locking device 30 also has a slotted actuating link 40. The latter has its movement plane oriented radially with respect to the longitudinal axis 20 (which corresponds to a telescoping direction of the boom 12). Specifically, the direction of movement of the slotted actuating link 40 runs in a tilting plane (i.e., from the bottom upward and vice versa in FIGS. 5 and 6) of the boom 12.

[0050] In addition to the plunger cylinder 34, the actuator 32 has lever kinematics 42 serving to deflect the rectilinear movement generated by the plunger cylinder 34 to the slotted actuating link 40 by means of rotation (see FIG. 3).

[0051] The slotted actuating link 40 is formed by a roughly I-shaped or omega-shaped plate in order to keep a recess 44 for the plunger rod 24 free. In each case a first slotted link groove 46 for the respective driver 36 and in each case a second slotted link groove 48 for the respective driver bolt 38 are introduced into said plate. Consequently, the slotted actuating link 40 has two first and two second slotted link grooves 46 and 48, respectively, in each case. The drivers 36 and the driver bolts 38 are coupled in their respective slotted link groove 46 and 48, respectively, by means of a respective slotted link rod 49 for adjustment radially with respect to the longitudinal axis 20, specifically in each case in the direction of the associated longitudinal side of the boom 12. In addition, the drivers 36 and driver bolts 38 are guided along their respective movement axis 35 in sliding rails 50 or sliding sleeves (not illustrated).

[0052] The driver bolts 38 are configured and provided so as, during a telescoping movement, to couple the telescope cylinder 22 to the boom extension segment 18 to be adjusted. The driver bolts 38 are therefore assigned to the locking device 30. The drivers 36 serve to adjust a respective locking bolt 52 under the action of the actuating force in order to lock (or: “bolt”) a boom extension segment 18 to the next outer boom extension segment 18 or to the main segment 16. Since the boom extension segments 18, as is known, also need to remain in their telescoped position after the telescoping movement, the locking bolts 52 are assigned to the boom extension segments 18. In other words, each boom extension segment 18 has a pair of locking bolts 52.

[0053] The drivers 36 and also the slotted actuating link 40 are configured in such a manner that the driver 36 can be coupled reversibly to the respective locking bolt 52. For this purpose, the respective driver 36 is designed in the manner of a claw. Specifically, the respective driver 36 has a T groove 54. The respective locking bolt 52 has, at its inner end, a T head 56 corresponding to the T groove 54 (see FIGS. 4 and 6). For the telescoping of a boom extension segment 18, first of all the telescope cylinder 22 is adjusted in such a manner that the locking device 30 is arranged in the “base region” of the corresponding boom extension segment 18. The boom extension segment 18 has a portion there that is also referred to as “bearing bracket 58” Sliding elements 60, inter alia, are arranged on the outer side of said bearing bracket 58 and slide on the inner side of the next outer boom extension segment 18 or of the main segment 16. In addition, the bearing bracket 58 has bolting eyes (not illustrated) for receiving the driver cylinders 38, and also has the locking bolts 52, which are guided in guide sleeves 62 (see FIGS. 4 and 5; only illustrated on the left side in FIG. 5).

[0054] If the telescope cylinder 22 “moves” with the locking device 30 into the region of the bearing bracket 58, the drivers 36 slide with the T grooves 54 over the T heads 56 of the locking bolts 52 and therefore grip the latter. In this state, the locking device 30 can adjust the locking bolts 52, i.e., can release (also: “pull”) them or push them outward along the movement axis 35 for the purpose of locking the respective boom extension segment 18. The locking bolts 52 are arranged on the bearing bracket 58 in such a manner that they are pressed under the action of an actuating spring, not illustrated specifically, into a locking position 64 in which they protrude on the outer side over the bearing bracket 58 (see FIG. 6) and therefore can couple to a corresponding bolting eye (not illustrated) of the next outer boom extension segment 18 or of the main segment 16.

[0055] The slotted actuating link 40 is, as is apparent from FIGS. 4 to 6, adjustable between three positions. An upwardly pulled end position, also referred to as tele-position 66, or telescoped position 66, is illustrated in FIG. 5. A downwardly pushed end position, also referred to as securing position 68, is illustrated in FIG. 6. A neutral position 70 arranged between the tele-position 66 and the securing position 68 is revealed in FIG. 4.

[0056] The second slotted link grooves 48 have two rectilinear curved portions which are at an angle to one another, and therefore have a single angle. The first slotted link grooves 46 have three rectilinear curved portions which are angled in relation to one another, and therefore have a double angle. The respective end-side curved portions of the slotted link grooves 46 and 48 are referred to as securing portion 72 and retraction portion 74. The third “middle” curved portion of the first slotted link groove 46 is referred to as neutral portion 76. The securing portions 72 are oriented parallel to the direction of movement of the slotted actuating link 40, whereas the retraction portions 74 are positioned facing obliquely inward counter to the push-out direction of the drivers 36 and of the driver bolts 38. As is apparent from the figures, the securing portions 72 and the retraction portions 74 of the first and second slotted link grooves 46 and 48 are oriented in an opposed manner with respect to the direction of movement of the slotted actuating link 40.

[0057] As a result, a diametrically opposed movement or adjustment of the driver bolts and of the locking bolts 38 and 52, respectively, takes place. In the tele-position 66, the locking bolts 52 are retracted into a release position 78 in which they do not couple to the outer boom extension segment 18 or main segment 16, i.e., the adjustment of the inner boom extension segment 18 is enabled. By contrast, the driver bolts 38 are pushed out into what is referred to as a carry-along position 80, in which they are coupled to the bearing bracket 58.

[0058] In the securing position 68 of the slotted actuating link 40 (see FIG. 6), the locking bolts 52, by contrast, are arranged in their locking position 64, whereas the driver bolts 38 are retracted into an empty running position 82. As a result, the telescope cylinder 22 can be moved without carrying along a boom extension segment 18, but with the boom extension segments 18 being secured because of the pushed-out locking bolts 52 (so-called “empty running”).

[0059] While the driver 36 moves inward or outward along the associated retraction portion 74, the driver bolt 38 remains in its locked position, i.e., the carry-along position 80 (the same also applies conversely), since the securing portion 72 is oriented parallel to the direction of movement of the slotted actuating link 40.

[0060] In the neutral position 70, the slotted link rods 49 of the drivers 36 are arranged in the region of the neutral portion 76. Said neutral portion is positioned more shallowly, i.e., at a smaller angle than the retraction portion 74 counter to the push-out direction, i.e., counter to the movement axis 35. This results in a smaller amount of friction when the locking bolt 52 is adjusted manually from the outside in the direction of its release position 78. The neutral portion 76 therefore permits emergency unlocking of the locking bolts 52. In addition, because of the position and the width of the first slotted link groove 46, the slotted link rod 49 has a comparatively greater amount of play along the movement axis 35 of the driver 36 in the region of the neutral portion 76. As a result, tolerance compensation in the region of the bearing bracket 58 and also the manual pushing in of the locking bolt 52 are simplified. A position of the locking bolts 52 during an emergency unlocking is illustrated in FIG. 8.

[0061] In order to be able to detect the position of the slotted actuating link 40, the locking device 30 has a position sensor 90. The latter is arranged in the region of the lever kinematics 42 and configured for detecting a rotational position. For this purpose, the position sensor 90 has two proximity switches 92 and an encoding disk 94 made from sheet metal with apertures as coding fields. By means of the proximity switches 92, the position of the encoding disk 94 is therefore identified from whether a coding field or a sheet metal wall lies opposite the applicable proximity switch 92. This design of the position sensor 90 is, as is known, robust against soiling by lubricant or hydraulic agent and—in particular because of the large elements selected—also against vibration.

[0062] In order additionally also to be able to check the actual position of the driver 36, the latter is also assigned a proximity switch 96. The latter is used to detect whether the driver 36 and therefore the locking bolt 52 are arranged in the locking position 64 and therefore the boom extension segment 18 is secured. This also permits a conclusion to be drawn as to whether the applicable boom extension segment 18 is arranged in its telescopic position as intended. This is because, during the telescoping of the boom extension segment 18, a control device 98 activates the locking device 30 in such a manner that the slotted actuating link 40, on moving into the bolting region of the outer boom extension segment 18 or of the main segment 16, is arranged in the neutral position 70. As a result, the drivers 36 and the locking bolts 52 can already bear against the inner side of the outer bolting region because of the play in the neutral portion 76 and because of the spring loading outward. The locking bolt 52 can therefore “feel” its associated bolting eye when the latter is “passed over.”

[0063] The plunger cylinder 34, as can be seen in FIGS. 3, 7 and 8, is spring-loaded by means of a first restoring spring 100 and a second restoring spring 101 in such a manner that, in the unpressurized state, it is returned to a main position and, in the process, puts the slotted actuating link 40 into its neutral position 70. For this purpose, the restoring spring 101 is coupled to a first piston rod 102 and a “spring cage 104” such that the first piston rod 102 is pushed back into the cylinder 106. The other, second restoring spring 101 is arranged between the cylinder 106 and the second piston rod 108 in such a manner that, in the unpressurized situation, said piston rod 108 is pulled out of the cylinder 106 (into its associated main position).

[0064] The spring cage 104 has a spring plate 110 and a linkage consisting of a plurality of supporting columns 112, here specifically three supporting columns, by means of which the spring plate 110 is positioned in relation to the cylinder 106. The first restoring spring 100 is arranged, specifically braced, between the spring plate 110 and a further spring plate 114, which is fastened to the first piston rod 102.

[0065] The supporting columns 112 are formed by threaded rods which permit a length setting for the spring cage 104, specifically an adjustment of the spring plate 110 in relation to the cylinder 106 and therefore setting of the pretensioning of the first restoring spring 100.

[0066] The second restoring spring 101 is arranged, specifically braced, between a cylinder-side spring plate 116, i.e., a spring plate connected to the cylinder 106, and a further spring plate 118 fastened to the second piston rod 108.

[0067] The first piston rod 102 bears a plunger piston 120 (giving its name to the plunger cylinder 34) (also see FIG. 8) which has longitudinal grooves 122 such that there is a fluidic connection between front piston end surface and rear-side piston ring surface. The plunger piston 120 is arranged in a first cylinder chamber 124 of the cylinder 106, which cylinder chamber is separated from a second cylinder chamber 128 by a partition 126. Independently of where a first hydraulic inlet 130 leads into the first cylinder chamber 124, when the first cylinder chamber 124 is pressurized, the plunger piston 120 is always extended counter to the first restoring spring 100.

[0068] A “normal”, in particular substantially circular-cylindrical, piston 132, which is attached to the second piston rod 108, is guided in the second cylinder chamber 128. In this case, a second hydraulic inlet 134 assigned to the second cylinder chamber 128 is arranged on the outer side, i.e., on that side of the piston 132 which faces the second piston rod 108. As a result, the piston 132 is pushed under pressure into the cylinder 106. In order to avoid counterpressure by a compressed air cushion in this case, a venting valve 136 is connected on the inner side, specifically in the region of the partition 126, to the second cylinder chamber 128.

[0069] In the state without hydraulic pressure, the plunger piston 120 and the piston 132, because of the two restoring springs, take up the positions illustrated in FIGS. 7 and 8 such that the plunger cylinder 34 has the above-mentioned neutral position.

[0070] In order now to put the slotted actuating link 40 into its securing position 68, i.e., to push the locking bolts 52 outward into their locking position 64 or to hold them therein, the first cylinder chamber 124 is charged with hydraulic pressure. As a result, the plunger piston 120 is displaced (specifically extended) by its associated actuating stroke 138. Via the lever kinematics 42, this rectilinear actuating movement is deflected and the slotted actuating link 40—in order to remain in the image according to FIGS. 1 to 6—is lowered, i.e., displaced downward. The second cylinder chamber 128 remains unpressurized here. The slotted link pins 49 of the drivers 36 slide along the securing portions 72 of the slotted link grooves in the process.

[0071] In order, by contrast, to put the slotted actuating link 40 into its tele-position 66, first of all the first cylinder chamber 124 is switched to an unpressurized state and the second cylinder chamber 128 is placed under pressure. As a result, the plunger piston 120 is “retracted” and the piston 132 extended by its actuating stroke 140. This actuating movement is in turn transmitted via the lever kinematics 42 to the slotted actuating link 40 and the latter is raised. The drivers 36 are thereby retracted; the locking bolts 52 are too and are therefore “released” or “unbolted”. By contrast, the driver bolts 38 are bolted to the next outer boom extension segment 18 or to the main segment 16, i.e., are extended.

[0072] The control device 98 is therefore configured to charge the two cylinder chambers 124 and 128 with hydraulic pressure basically independently of one another. Preferably, however, the one cylinder chamber 124 or 128 is switched to an unpressurized state together with the other cylinder chamber 128 or 124 being pressurized.

[0073] The subject matter of the invention is not restricted to the above-described exemplary embodiment. Rather, further embodiments of the invention can be derived by a person skilled in the art from the above description.

[0074] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0075] 1 Mobile crane [0076] 2 Undercarriage [0077] 4 Wheel [0078] 6 Cockpit [0079] 8 Superstructure [0080] 10 Vertical axis [0081] 12 Boom [0082] 14 Rocker axis [0083] 16 Main segment [0084] 18 Boom extension segment [0085] 20 Longitudinal axis [0086] 22 Telescope cylinder [0087] 24 Piston rod [0088] 28 Cylinder [0089] 30 Locking device [0090] 32 Actuator [0091] 34 Plunger cylinder [0092] 35 Movement axis [0093] 36 Driver [0094] 38 Driver bolt [0095] 40 Slotted actuating link [0096] 42 Lever kinematics [0097] 44 Recess [0098] 46 Slotted link groove [0099] 48 Slotted link groove [0100] 49 Slotted link rod [0101] 50 Sliding rail [0102] 52 Locking bolt [0103] 54 T groove [0104] 56 T head [0105] 58 Bearing bolt [0106] 60 Sliding element [0107] 62 Guide sleeve [0108] 64 Locking position [0109] 66 Tele-position [0110] 68 Securing position [0111] 70 Neutral position [0112] 72 Securing portion [0113] 74 Retraction portion [0114] 76 Neutral portion [0115] 78 Release position [0116] 80 Carry-along position [0117] 82 Empty running position [0118] 90 Position sensor [0119] 92 Proximity switch [0120] 94 Encoding disk [0121] 96 Proximity switch [0122] 100 Restoring spring [0123] 101 Restoring spring [0124] 102 Piston rod [0125] 104 Spring cage [0126] 106 Cylinder [0127] 108 Piston rod [0128] 110 Spring plate [0129] 112 Supporting column [0130] 114 Spring plate [0131] 116 Spring plate [0132] 118 Spring plate [0133] 120 Plunger piston [0134] 122 Longitudinal groove [0135] 124 Cylinder chamber [0136] 130 Hydraulic inlet [0137] 132 Piston [0138] 134 Hydraulic inlet [0139] 136 Venting valve [0140] 138 Actuating stroke [0141] 140 Actuating stroke