Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
  • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
  • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
  • F15B11/20—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors controlling several interacting or sequentially-operating members
  • F15B11/205—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors controlling several interacting or sequentially-operating members the position of the actuator controlling the fluid flow to the subsequent actuator
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B66—HOISTING; LIFTING; HAULING
  • B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
  • B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
  • B66C23/62—Constructional features or details
  • B66C23/64—Jibs
  • B66C23/70—Jibs constructed of sections adapted to be assembled to form jibs or various lengths
  • B66C23/701—Jibs constructed of sections adapted to be assembled to form jibs or various lengths telescopic
  • B66C23/705—Jibs constructed of sections adapted to be assembled to form jibs or various lengths telescopic telescoped by hydraulic jacks

Definitions

• the present invention relates to an extendible boom comprising a plurality of telescopical boom sections which are displaceable into and out of each other by means of double- acting hydraulic units, of which each one separately comprises a cylinder and a hollow piston rod with a piston that divides the interior of the cylinder into two chambers, namely a piston side chamber between the piston and a first gable portion of the cylinder and a piston rod chamber between the piston and a second gable portion with a hole through which the piston rod is reciprocally displaceable, two main conduits being arranged between co-operating, adjacent hydraulic units, of which conduits a first one has the purpose of feeding oil or a hydrau ⁇ lic medium from an inner hydraulic unit to the piston side chamber in the outwardly next unit in order to push the piston rod out of the cylinder of the latter unit, while the other conduit has the purpose of feeding oil to the piston rod chamber in the same cylinder from the inwardly located unit in order to push the piston rod into it.
• Extendible booms of the type generally defined above are often included as jib levers in cranes.
• a primary object of the invention is to create a boom whose hydraulic units for a sequential adjustment of the different telescopic boom sections are of such a nature that they are capable of reliably holding their piston rod in the pushed-out end position as long as the piston rod in each outwardly located hydraulic unit is not pushed into its inner end position.
• a further object is to achieve this sequential adjustment automatically and in a mechanical way, i.e., without necessitating for instance an electric regulation of valves.
• a further object of the invention is to realize the problem solution by means of hydraulic units which are hydraulically connected to each other via stationary or stiff conduits. According to the invention, at least the primary object is attained by the features as defined in the characterizing clause of claim 1. Preferred embodiments of the invention are further defined in the dependent claims.
• Fig 1 is a schematic longitudinal section through a hydraulic unit included in an extendible boom according to the invention
• Fig 2 also shows schematic longitudinal sections through four hydraulic units included in an extendible boom for the adjustment of equally many telescopic boom sections, three units being made in the way shown in figure 1, while an outer unit being of a simpler construction, and the piston rods of all units being shown in a pushed-in, inner end position
• Fig 3 shows analogous longitudinal sections of the same hydraulic units as in figure 2, but showing the piston rod of the innermost unit pushed out to an outer end position
• Fig 4 is an illustration corresponding to figure 3 showing how the pushing-out of the piston rod of the second innermost hydraulic unit has been started
• Fig 5 is an enlarged longitudinal section through a useful, constructive embodiment of the hydraulic unit according to figure 1, only the outer portion of the cylinder being shown and the piston rod and the associated piston being illustrated in the proximity of, although at some distance from an outer end position
• ig 6 is a longitudinal section corresponding to figure 5 showing the piston rod fully pushed-out to the outer end position
• Fig 7-9 are enlarged cross-sections A, B and C, respectively, in figure 6.
• reference numeral 1 generally designates a hydraulic unit or a so called hydraulic cylinder which comprise a cylinder 2 as such, a piston 3 and a piston rod 4.
• the piston 3 divides the interior of cylinder 2 into two chambers, namely piston side chamber 5 between the piston and a first gable portion or bottom 6, and a piston rod chamber 7 between the piston and a second gable portion 8 in which there is a hole 9 through which the piston rod 4 is reciprocally movable.
• a first main conduit 10 is connected to the piston rod chamber 7.
• the piston rod 4 is hollow by comprising a tubular portion 12 that confines a cavity 13.
• piston rod 4 At its free end, piston rod 4 has a head 14. In the area of this head, two further hydraulic conduits designated 10' and 11', respectively, are connected to the piston rod.
• FIG 2 illustrates h an extendible boom according to the invention comprises severa further hydraulic units 1', 1" and 1"' beside the unit 1.
• the individual telescopic boom sections that togethe form an extendible boom, are not shown in the drawings, in practice the first hydraulic unit 1 is mounted on an inner boo section, the head 14 on the piston rod of the unit being connected to the second innermost boom section on which in turn the hydraulic unit 1' is mounted.
• the hydraulic unit 1' has the head 14 ' of the piston rod connected with the next tele ⁇ scopic boom section, and so forth. All the hydraulic units with the exception of the outer unit 1 '" are of the design shown in figure 1.
• the outer hydraulic unit 1'" is of a simpler construc ⁇ tion and comprises beside a cylinder merely a simple piston and a simple piston rod.
• the conduits 10', 11' hydraulically connect the unit 1 with the unit 1' .
• the conduits 10", 11" connect the unit 1' with the unit 1", and so forth.
• carriers designated 15 are connected to the free ends of the piston rods to all hydraulic units except the unit 1.
• a transmission element 16 is arranged within the hollow piston rod 4, which element co-operates in the region of its inner end with a locking device designated by reference numeral 17 in its entirety, and which at its opposite end may at least indirectly be activated by a carrier 15 of an adjacent hydraulic unit.
• the transmission element 16 has the shape of a tube whose interior forms a duct or intermediate conduit 18.
• the locking device 17 comprises one or several radially movable taps arranged to, when in an active locking state, engage into a seat 19, which in the example is illustrated in the form of a circumscribing groove on the inside of a ring-shaped flange 20 that protrudes from the inside of the gable portion 8.
• the tube 16 has a wedge body 21 that has an oblique or conical surface arranged to cooperate with a correspondingly oblique surface on the locking tap or taps, more specifically in such a way that each locking tap is radially displaced outwardly when the wedge body 21 is distanced from the piston 3.
• the wedge body 21 is accommodated in a chamber 22 inside the piston portion.
• the chamber 22 is sealed relative to the cavity 13 in the piston rod 4 by a gasket 23.
• the chamber 22 communicates with the piston rod chamber 7 via a constantly open transverse ho] e 24. Further, chamber 22 commur. ' cates with the duct 18 within tube 16 via a second transverse hole 25 in the wall of the tube.
• the piston 3 further comprises a non-return or clack valve which is schematically exemplified in the form of a sphere 27 that is loaded by a spring force, as illustrated in the form of a pressing coil spring 27'.
• a non-return or clack valve which is schematically exemplified in the form of a sphere 27 that is loaded by a spring force, as illustrated in the form of a pressing coil spring 27'.
• the ball 27 is shown in a closing state in which it impedes communication between the piston side chamber 5 and a duct 28 extending through the piston, which duct leads to the cavity 13 of the piston rod.
• the clack valve may be opened against the force of spring 27', permitting communication between chamber 5 and duct 28. This happens when the piston arrives to its outer end position and the free end of tap 29 gets in contact with the annular flange 20.
• conduit 10' is connected to an communicates with cavity 13 in the piston rod 4.
• the tube 16 has on one hand a trans- verse hole 30 in the tube wall, and on the other hand a first auxiliary piston 31.
• the transverse hole 30 is located in a chamber 32 which on one hand is sealed relative to the cavity 1 by a gasket 33, and on the other hand by a second gasket 34 relative to a space 35 in which the first auxiliary piston 31 i reciprocally movable.
• the auxiliary piston 31 divides the space 35 into two part-chambers 36, 37.
• Auxiliary piston 31 is actua ⁇ ted by a spring force that is schematically illustrated in the form of a pressing coil spring 38, which constantly strives to move the auxiliary piston in a direction outwards, towards the free end of the piston rod.
• Part-chamber 37 is also delimited b a second auxiliary piston 39 which is reciprocally movable in a course 40 in the piston rod head 14.
• Part-chamber 37 is filled with a hydraulic medium, preferably in the form of a grease th may be filled up via a nipple 41.
• a pressure is upheld in the grease mass, which guarantees that the auxiliary piston 31 and the tube 16 are kept in an inner e position against the force of the spring 38. In this state, the locking device 17 is inactive.
• reference numeral 42 designates a hole in which suitable means may be placed, for instance bolts, for mechanical fastening of the free end of the piston rod to an adjacent telescopic boom section or its hydraulic unit.
• the directional valve connects the conduit 10 with the pump, while the conduit 11 is kept open relative to the tank. Oil is fed into the piston side chamber 5 and sets the piston 3 into motion towards the outer end position. Thereby, any oil in the piston rod chamber 7 is evacuated to the tank via the conduit 11.
• the displacement of the piston the whole way from the inner end position to the outer end position is secured by means of the clack valve 27, which during the displacement prevents any communication between the piston side chamber and the duct 28.
• the oil in the piston rod chamber 7 is forcibly pressed out into the conduit 11 in spite of the fact that the communication with the conduit 11' is open via the transverse hole 24, the chamber 22, the transverse hole 25, the tube conduit 18, the transverse hole 30 and the chamber 32, because of the fact that the piston rod chambers in all the other hydraulic units 1', 1" and 1'" are filled with oil.
• the locking device 17 is located opposite to the seat 19.
• the carrier tap 29 opens the clack valve 27; something that allows communication between the piston side chamber 5 and the duct 28.
• oil may be fed from the chamber 5 into the ring- shaped cavity 13 inside the piston rod and further through the conduit 10' into the piston side chamber in the adjacent hydrau lic unit 1'.
• a displacement is initiated of the piston 3 ' of the latter unit in the direction towards its outer end position, resulting in the piston rod 4' being pushed out of th associated cylinder 2' .
• the carrier 15 is distanced from the free end or head 14 of the first piston rod 4 and liberates the auxiliary piston 39 so tha it may move outwardly, out of the appurtenant course.
• the pressure in part-chamber 37 is reduced so that the spring 3 forces the auxiliary piston 31 and the tube 16 to move towards an outer end position.
• wedge body 21 actuat the locking device 17 so that the locking taps of said device engage with the seat 19.
• the device 17 locks t piston 3 mechanically in its outer end position.
• the oil from the conduit 11 may be fed via the previously men ⁇ tioned flow path (transverse hole 24, chamber 22, transverse hole 25, tube duct 18, transverse hole 30 and chamber 32) to the conduit 11' and further through the hydraulic units 1', 1" and the conduits 11" and 11"' to the piston rod chamber of the unit 1"'.
• the piston 3'" is displaced from its outer end position to its inner end position. Since the clack valves in all mechanically locked pistons are open, the oil in the piston side chamber of the unit 1'" may be evacuated via the conduits 10'", 10" and 10 to the tank.
• each controlled hydraulic unit mechanically locks the associated piston rod in a fully pushed-out state as soon as the pushing-out of the ; iston rod in the outwardly adjacent hydraulic unit is smarted, a distinct and reliable sequential adjustment of the different telescopic boom sections is attained independently of whether the boom is extended or contracted.
• stiff or stationary hydraulic conduits may be arranged between co-operating units, for instance in the form of tubes.
• the two conduits between adjacent units are connected to on one hand only one piston rod head and on the other hand to only one cylinder.
• the invention makes it possible to connect an unlimited number of cylinders with each other for the adjustment of an arbitrary number of telescopic boom sections.
• the clack valve 27 in this case is opened by an auxiliary piston 43 that is provided in a chamber filled with a hydraulic medium in the form of grease.
• the pressure in the grease is increased so that the piston 43 is se in motion and distances the valve ball from its associated seat
• the locking device 17 comprises three peripherically equidistantly separa ⁇ ted, radially movable locking taps.
• auxiliary piston 39 which is actuatable by a carrier 15 of an adjacent hydraulic unit and has the purpose of setting in motion the tube 16 that serves as a transmission element, in this case is placed at a certain distance from the part-chamber 37 in which the auxiliary piston 31 is movable.
• the positioning of the auxiliary piston 39 is not critical. On the contrary, it may be placed f distant from the piston rod head as such and be connected with the part-chamber 37 via a suitable conduit.
• auxiliary piston 31 is not connected to any spring (cf. spring 38 in figure 1), but instead influenced by the internal oil pressure in the piston rod 11 which is always striving at pushing the auxiliary piston towards the outer end position.
• the invention is not restricted only to the embodiments as described and shown in the drawings.
• it is feasible to provide a separate transmission element within the hollow piston rod, for adjusting the locking device although the tube serving as an intermediate conduit advantageously is used as a trans ⁇ mission element.
• Opening and closing of the clack valve in the main piston of the cylinder may be effected in another way than by means of the schematically shown spring 27' and auxiliary piston 43.
• the concrete design of the locking device 17 per se may be varied within wide limits.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• General Engineering & Computer Science (AREA)
• Actuator (AREA)
• Jib Cranes (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (6)

Cited By (6)

Families Citing this family (2)

Citations (3)

• 1995
  • 1995-06-08 SE SE9502099A patent/SE504463C2/sv not_active IP Right Cessation
• 1996
  • 1996-05-09 WO PCT/SE1996/000606 patent/WO1996041764A1/en active IP Right Grant
  • 1996-05-09 DE DE69612380T patent/DE69612380T2/de not_active Expired - Fee Related
  • 1996-05-09 AT AT96915286T patent/ATE200266T1/de not_active IP Right Cessation
  • 1996-05-09 AU AU57095/96A patent/AU5709596A/en not_active Abandoned
  • 1996-05-09 EP EP96915286A patent/EP0835220B1/en not_active Expired - Lifetime

Patent Citations (3)

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