EP0224446A2 - Hydraulische Lastbegrenzungsvorrichtung für hydraulische Krane - Google Patents

Hydraulische Lastbegrenzungsvorrichtung für hydraulische Krane Download PDF

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Publication number
EP0224446A2
EP0224446A2 EP86830202A EP86830202A EP0224446A2 EP 0224446 A2 EP0224446 A2 EP 0224446A2 EP 86830202 A EP86830202 A EP 86830202A EP 86830202 A EP86830202 A EP 86830202A EP 0224446 A2 EP0224446 A2 EP 0224446A2
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EP
European Patent Office
Prior art keywords
valve
line
pressure
cylinder
way
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP86830202A
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English (en)
French (fr)
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EP0224446A3 (en
EP0224446B1 (de
Inventor
Andrea Storci
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Oil Control SpA
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Oil Control SpA
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Filing date
Publication date
Priority claimed from IT40128/85A external-priority patent/IT1187219B/it
Priority claimed from IT40135/85A external-priority patent/IT1202291B/it
Priority claimed from IT40016/86A external-priority patent/IT1189792B/it
Application filed by Oil Control SpA filed Critical Oil Control SpA
Publication of EP0224446A2 publication Critical patent/EP0224446A2/de
Publication of EP0224446A3 publication Critical patent/EP0224446A3/en
Application granted granted Critical
Publication of EP0224446B1 publication Critical patent/EP0224446B1/de
Expired legal-status Critical Current

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    • 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
    • B66C23/88—Safety gear
    • B66C23/90—Devices for indicating or limiting lifting moment

Definitions

  • the invention described herein relates to a hydraulic load limiting device for hydraulic cranes.
  • a device as disclosed is intended for application to cranes of the general type consisting of a column to which a boom with one or more folding and/or telescopic stage or stages is attached, the single stage being operated by a relative hydraulic cylinder.
  • One of the requirements of safety regulations existing in numerous countries the world over, is that any movement in the boom liable to overload the crane by exceeding its maximum rated lift capacity, must be inhibited.
  • any subsequent movement in the boom that would lead to an increase in the load- related moment of force must be disallowed; more exactly, any movement whereby a telescopic boom is further extended, and any rotational movement of the boom stages such as distances the load from the crane's slewing axis, must be prevented from taking place.
  • an increase in moment of force generated by the load is converted, in substantially linear manner, into a build-up of pressure in the rear end of the hydraulic cylinder which operates the hinged boom stage, or supports the hinged boom assembly; accordingly, control and subsequent limiting of the moment of force generated by the load is effected by monitoring pressure of the fluid that impinges on the rear end of the cylinder in question, and limiting it in relation to a given preset level.
  • the prior art embraces devices in which use is made of an electrical signal, relayed from a pressure switch triggered by pressure in the rear end of the cylinder, to energize the solenoids of valves that prevent further ingress of hydraulic fluid to the cylinders such as might lead to an increase in the moment of force generated by the load.
  • Prior art devices also offer a level-sensing system by means of which to produce an electrical signal, triggered by the angle of the boom above or below horizontal, such as will operate means whereby movement of the boom is enabled insofar as the load- related moment of force will diminish, and inhibited where bound to increase -i.e., when the load matches the maximum rated lift capacity of the crane.
  • Cranes are generally utilized and parked outdoors, and faultless operation of the above devices is very often jeopardized by weather conditions.
  • a further drawback of prior art devices is that the wiring required for their operation can deteriorate and fail with the passage of time, and with use of the crane.
  • boom level-sensing systems involves considerable complication of the hydraulic load limiting circuit.
  • One object of the invention described herein is that of overcoming the drawbacks mentioned above, providing a device that can respond to all such safety requirements as are envisaged under law, whilst making no use whatever of electrical circuits, whether for relaying control signals or for actuating the valves which shut off flow of hydraulic fluid to the boom cylinders.
  • a further object of the invention is that of providing a device that will not be sensitive to any accidental surge in the moment of force generated by the load, and which will cut in at the precise overload setting selected, whatever the operating conditions.
  • Another object of the invention is that of providing a device which, at maximum rated lift capacity, will inhibit any movement in the crane liable to produce overload conditions, regardless of the configuration of the crane at that instant, and do so without any need for indication of the angle at which the boom stages happen to be disposed.
  • a clear advantage of the device disclosed is that it is all-hydraulic, and uses the same source of energy for its operation (pressurized fluid) as that used by the crane as a whole; such a feature is especially advantageous in terms of circuit design and cost.
  • a device according to the invention employs hydraulic on-off and/or switching valves which respond to a pressure signal from one of the boom cylinders, and produce a hydraulic control signal used either directly or in conjunction with a hydraulic level sensing system to pilot hydraulic valves installed on the lines connecting with the boom cylinders, to the end of shutting off pressure flow to the cylinders whenever further extension or retraction would cause the boom to assume a configuration whereby maximum rated lift capacity is exceeded.
  • the crane illustrated in the drawings consists of a column 1, a first boom stage 2 which is hinged to the top of the column 1 and rotated about its pivot by a hydraulic cylinder 4, and a second boom stage 3 which is both hinged and telescopic, rotated about its pivot by one hydraulic cylinder 5, and extended and retracted telescopically by a further hydraulic cylinder 6.
  • the hydraulic cylinders are connected to a directional control valve assembly denoted 15, each single section of which, when operated, provides a relative cylinder with fluid supplied under pressure from a pump 14.
  • 4a, 5a and 6a denote lines connecting each section of the control valve with the rear end of the relative cylinder
  • 4b, 5b and 6b denote similar lines connecting with the rod end of each cylinder
  • the 'a' and 'b' lines of each circuit thus alternate between pressure and return functions, according to the position of the control valve.
  • 4c, 5c and 6c denote respective holding valves installed one in each of the cylinder circuits to the end of preventing jerky descent of the load.
  • the device as embodied in figs 1, 4, 10, 11 and 12 comprises two-way two-position hydraulic valves, denoted 7a, 7b, 8a, 8b and 9, which are installed in the circuits operating the two hinged cylinders 4 and 5, and in the line connecting with the rear end of the telescoping cylinder 6, respectively.
  • each such valve blocks pressure flow through the relative line while allowing return flow through the same line; in the second position, flow is permitted in either direction.
  • Each valve is held in the second position by pressure of the fluid through the line upstream of the valve itself, and biased toward the first position by a respective spring 17a, 17b, 18a, 18b and 19, as well as being piloted into the first position by a hydraulic control signal described in detail below.
  • the device as embodied in figs 1 & 4 comprises load- sensing means incorporating a two-way two-position hydraulic response valve 10, first position open, second position closed.
  • the first port of the valve 10 connects with the pump 14, and the second port with a first send line 11 that carries the hydraulic control signal utilized for direct or indirect operation of the shut-off valves 7a, 7b, 8a, 8b and 9.
  • the response valve 10 is biased into normally closed position by a spring 10a, and piloted to open in direct fashion by a pressure signal generated in the rear end of the first stage cylinder 4 and carried to the valve 10 by a relative line 22; the valve 10 is thus operated directly by pressure impinging on the rear end of the cylinder 4 which, it will be remembered, is proportional to the moment of force generated by the load.
  • the device as embodied in figs 1 & 4 also comprises level sensing means in the form of a three-way hydraulic valve 25 with a ball 26 that is free to float within the valve chamber.
  • the first port of such a valve is located in the side wall of the chamber and remains permanently open, whereas the second and the third port are located at either end of the chamber, which also offer relative seats in which the ball 26 may register.
  • the valve 25 is made fast to the third stage 3 of the boom, and thus serves to indicate the position of boom as regards the angle assumed.above or below horizontal; more exactly, indication of the position A or B of the boom (see fig 1) is made possible by the fact that the ball 26 will shift toward one or other end of the valve chamber, according to the angle assumed by the boom.
  • the first port of the level sensing valve 25 is connected to the first send line 11, whereas the second and the third ports are connected to a second and a third send line 12 and 13, respectively.
  • the hydraulic signal utilized for operation of the valve denoted 9 is taken off the first send line 11.
  • the valves 7a and 8a installed on the lines connecting with the rear ends of the two respective hinged cylinders 4 and 5 are operated by a hydraulic signal supplied through the second send line 12
  • the valves 7b and 8b on the lines connecting with the rod ends of the same cylinders are operated by a signal supplied through the third send line 13.
  • the mechanical structure of a given crane may be such that no linear relationship can exist between pressure in the rear end of the cylinder 4 and the moment of force generated by the load; the result is that certain movements of the boom may overload the crane beyond rated lift capacity without rear end pressure in the cylinder 4 actually registering at the maximum setting envisaged.
  • Fig 2 illustrates how the second valve 10' would be incorporated, where appropriate.
  • the element of the response valve 10 is piloted to close by a pressure signal taken off the rod end line 4b, and the area of the valve element on which this signal impinges differs from the area invested by the signal from the rear end line 4a to an extent commensurate with the difference in piston area between the rod end and rear end of the cylinder 4.
  • Fig 3 illustrates how the response valve 10 may be embodied so as to remain unaffected by pilot .pressure through the rod end line 4b of the cylinder circuit.
  • the embodiment of fig 1 also comprises a manually operated hydraulic unloading valve 20 installed in normally closed configuration between the sensing line 22 and the return line, the purpose of which is described in detail below.
  • each send line is provided with a respective restriction connecting to tank.
  • one has a third two-way two-position hydraulic response valve 10", first position open, second position closed, biased into its normally closed position by a spring 10a", and piloted to open in direct fashion by a pressure signal supplied through the sensing line 22.
  • the first port of the valve 10" connects with the pump 14, and the second port with a fourth send line 51,
  • the first response valve 10 will be piloted to open whenever pressure impinging on the rear end of the cylinder 4 and relayed through the sensing line 22 reflects maximum rated lift capacity of the crane, whereas the third shut-off valve 10" is caused to open by a pressure level marginally in excess of this setting.
  • This second embodiment of the device also incorporates a three-way two-position switching valve 52, a first port of which is connected to the first send line 11, the second and third ports being connected respectively to a fifth and a sixth send line 53 and 54 which supply the control signal for operation of two of the shut-off valves 7b and 7a, respectively; signals for operation of the valves denoted 8a and 8b continue to be supplied by the second and third send lines 12 and 13.
  • the switching valve 52 is biased by a spring 55 into first position, whereby first and second ports are connected, and piloted into the second position, in which the first and third ports connect, by a signal supplied through the fourth send line 51.
  • sensing means comprise a three-way two-position valve 41 which is biased by a spring 45 into its first position, whereby first and third ports are connected; the valve,41 is piloted into its second position, in which second and third ports are connected, by a pressure signal taken off from the rear end of the first cylinder 4 and routed to the valve by way of a branched leg 22a of the sensing line 22. Shift of the valve from first to second position occurs whenever the signal reaches a preset pressure level marginally below that which reflects maximum rated lift capacity of the crane.
  • the sensing means in figs 10 and 11 further comprise a four-way two-position valve 42 biased by a spring 46 into its first position, in which the first port connects with the third and the second port connects with the fourth; the valve 42 is piloted into its second position, in which the first port connects with the fourth, and the second port with the third, by the same pressure signal as aforementioned, which is routed to the valve by way of the remaining leg 22b of the branched sensing line 22. Shift of the valve from first to second position occurs whenever the signal reaches a pressure level reflecting the maximum rated lift capacity of the crane.
  • the first port of both valves 41 and 42 is connected to tank; the second and third ports of the valve denoted 41 are connected to the pump 14, and to the second port of the valve denoted 42, respectively.
  • the third port of the four-way valve 42 connects via a send line 47 with the pilot circuits of two of the shut-off valves 7b and 8b; the fourth port of the valve connects via a further send line 48 with the pilot circuits.of the shut-off valves denoted 7a and 8a.
  • the pilot circuit of the remaining shut-off valve 9 connects via an additional send line 49 with the third port of the three-way valve 41.
  • the third port of the four-way valve 42 connects by way of the first send line 47 with the pilot circuits of valves 7a and 8a; the fourth port of the valve connects via the second send line 48 with the pilot circuits of valves 7b and 8b.
  • the pilot circuit of the remaining shut-off valve 9 connects via an additional send line 49 with the third port of the three-way valve 41, as in the previous embodiment.
  • the leg denoted 22b which branches from the sensing line 22 incorporates a check valve 44a allowing flow of hydraulic fluid, hence of the pressure signal, toward the four-way valve 42.
  • valve 44 denotes a pressure balancing valve that connects the one leg 22a of the branched sensing line 22 with a point on the remaining leg 22b between the check valve 44a and the four-way valve 42. Biased into the normally closed position by a spring, the valve 44 is obliged to close by pressure through the one leg 22a, and piloted to open by pressure through the remaining leg 22b.
  • the pressure balancing valve 44 is set in such a way as to connect the two legs 22a and 22b of the sensing line 22 with one another whenever the difference in pressure between the two is marginally greater than the difference between the respective pressure levels that produce shift of the four-way load sensing valve 42 and the three-way load sensing valve 41 from first to second position.
  • the purpose of the valve 44 in question is to restore normal conditions in the limiting device once both sensing valves 41 and 42 have been piloted into second position, and will become clear in due course. Return of the four-way valve 42 to the first position is enabled only after the three-way valve 41 has been returned to first position.
  • the embodiment of fig 10 comprises a normally closed manual unloading valve 43 which connects the sensing line 22 to tank, and performs the identical function to that denoted 20 aforedescribed.
  • Sensing means in the embodiment of fig 12 are the same as those illustrated in fig 10, with the exception that the manual unloading valve 43 is dispensed with; valves and connections serving the second and third cylinder circuits 5a-5b and 6a-6b likewise remain the same.
  • the line denoted 4b is connected directly to the rod end of the first cylinder 4, and exhausted to tank by a relief valve 60 whenever pressure through the line itself rises beyond the relative setting; the relief valve 60 is set to operate independently of the limiting device.
  • Shut-off valves 7a and 7b are connected to the rear end line 4a in series, and a further relief valve 61 downstream of the second valve 7b will exhaust the rear end to tank whenever pressure through the line 4a rises above the valve setting; in this instance, the valve 61 is set to a pressure marginally in excess of that reflecting maximum rated lift capacity of the crane.
  • the pressure signal that pilots the valves denoted 7a and 8a is supplied through the second send line 48, whilst that piloting the valves denoted 7b and 7b is supplied through the first send line 47.
  • the signal which pilots the remaining shut-off valve 9 continues to be supplied via the third send line 49.
  • 63 denotes a second three-way two-position valve maintained normally in the first position, in which first and third ports are connected; the valve is piloted into its second position by pressure flow from the pump 14, thereby connecting the second and third ports, whenever there is a rise beyond the maximum pressure envisaged during retraction of the cylinder rods, hence descent of the boom.
  • Retract pressure is easily quantifiable, corresponding as it does to descent of the boom with no load, and in any event will be considerably lower than the pressure level reflecting maximum rated lift capacity of the crane.
  • the three ports of the valve 63 are connected thus: first port to tank; second port direct to the pump 14; and third port to a pilot line 64. Pressure registering through the pilot line 64 will be transmitted to the four-way sensing valve 42, on .which it impinges in the same direction as the force exerted by the spring 46 and thus assists in biasing the valve 42 into first position.
  • valves 10 and 10' in the embodiments of figs 1 and 2 will be normally closed. Supposing that maximum rated capacity is reached in the configuration denoted A in fig 1, then the pressure signal deriving from the rear end of the first cylinder 4 will open the valve denoted 10, connecting the pump 14 to the first send line 11, in which a hydraulic control signal is duly set up. Needless to say, in the event of there being two load sensing valves 10 and 10', the control signal will be set up by whichever valve opens first.
  • the control signal acts directly on the telescoping shut-off valve 9, preventing it from opening even though the relative control valve spool may be moved into the position whereby fluid is directed through the respective line 6a; clearly, any further extension of the telescoping cylinder 6 would increase the load, regardless of the angle A or B. No load limiting components whatever are incorporated into the rod end line 6b of the cylinder 6 in question, since normal retraction reduces the load automatically.
  • the control signal is fed through the first send line 11 and into the level-sensing valve 25, the ball 26 of which blocks the second send line 12 and opens up the third send line 13, given the position of the boom.
  • the third send line 13 being open, the control signal impinges on the shut-off valves 7b and 8b installed on the rod end lines to the first and second cylinders 4 and 5; pressure reaching the rod end of either cylinder at this point would turn the relative boom stage toward the ground and increase the load beyond the permissible limit.
  • valves 7a and 8a controlling the lines to the rear end of the two cylinders 4 and 5 are in receipt of no such load limiting signal, and shift of the relative control valve spools will direct fluid to the service as normal; ingress of fluid into the rear end will in fact raise the boom, reducing the load.
  • valve denoted 10 will once again be opened by the signal originating from the rear end of the first cylinder 4; as far as the telescoping cylinder 6 is concerned, the same situation obtains as described above.
  • the two-way sensing valve 10 closes, and pressure in the send lines is exhausted via the restrictions in readiness for further operation of the entire set of load limiting valves.
  • a spring-loaded check valve 30 is installed upstream of the manual facility; this will close whenever the difference in pressure between inlet and outlet ports of the valve is of an order greater than the bias spring setting.
  • the control signal will be relayed to one or other of the two second stage shut-off valves 8a or 8b, depending on the angle of the second boom stage 3 and the corresponding state of the level-sensing valve 25.
  • the signal will be transmitted through the third send line 13 to the rod end valve 8b, thereby disallowing downward rotation of the boom stage 3 and preventing resultant increase of the load; no such signal will impinge on the rear end valve 8a, since upward rotation of the same stage 3 will automatically reduce the load and is thus permissible.
  • the load limiting device prevents overload on the crane at the moment that its maximum rated lift capacity is either matched or exceeded. It will be obvious to a person skilled in the art, however, that a load in excess of maximum rated capacity can be avoided altogether simply by setting the one load sensing valve 10" at a pressure to match the maximum load, and setting the other 10 at a level marginally below this same pressure.
  • the sensing valves 10" and 10 will reassume closed position, and control signal pressure through the send line 11 and the various passages leading to the shut-off valves 7a, 7b, 8a, 8b and 9 will exhaust via their relative restrictions, returning the device to its original configuration in which all movements are enabled. It will be observed that the switching valve 52 returns to first position only when the valve denoted 10 has likewise been returned to closed position, since this is the only situation in which pressure can be exhausted from the send line 11.
  • the switching valve 52 memorizes second position until otherwise instructed by a return to normal operating conditions.
  • arrival at maximum rated lift capacity causes the signal set up by the load sensing valve 10 to be transmitted direct to the valves denoted 7b and 9, and neither downward rotation of the first stage 2 nor telescoping of the second stage 3 are allowed, whatever their position; downward rotation of the second stage 3 will be inhibited only where the boom is angled above horizontal as in fig 9.
  • the level-sensed control signal will be relayed via the send line 13 to the valve denoted 8b, which blocks pressure flow to the rod end of the relative cylinder 5.
  • the relative valve 8b will be in receipt of no control signal by reason of the fact that the level-sensing valve 25 blocks the send line 13, and downward rotation is therefore permitted.
  • upward rotation of the stage 3 will be disallowed only where the movement is such as to produce an increase in load, reflected by a build-up of rear end pressure in the relative cylinder 5 and consequent operation of the relief valve 58.
  • a further reduction in load produces a further drop in pressure through the leg of the branched sensing line denoted 22a, and once the difference in pressure between the two branches 22b and 22a reaches a preset level, which at all events will be higher than the difference between the respective pressure levels causing shift of the three-way and four-way sensing valves 41 and 42 from first to second position, then the pressure balancing valve 44 will open so as to exhaust pressure from the leg denoted 22b and enable the four-way sensing valve to return to first position.
  • Flow to and from the service through the rear end line 4a is controlled by the valves denoted 7a and 7b, respectively; accordingly, shift of the three-way and the four-way load sensing valves 41 and 42 to second position disallows flow to the service and from the service, respectively, any excess pressure through the line 4a being exhausted by the relief valve 61.
  • the second advantage is that the unloading valve 43 of fig 10 becomes unnecessary. With arrival of the cylinder 4 at its stroke limit, excess pressure becoming trapped in the stretch of line 4a connecting the cylinder with the holding valve 4c (pressure which is exploited for operation of the load sensing valves 41 and 42) can be relieved by connecting the free rod end line 4b with pressure; the load holding valve 4c can thus be piloted to open, and the excess pressure relieved.
  • valve denoted 63 provides a further significant advantage.
  • circuit pressure should rise beyond the maximum pump rating calculated to occur during retraction (the situation in question can arise only during extension, clearly enough)
  • the valve 63 will be shifted into second position, thereby relaying a signal to the four-way load sensing valve 42 that prevents its moving from first to second position under any circumstance. More exactly, the valve 63 remains inoperative as long as the cylinders are retracting, whereas on the extending stroke, the moment that maximum rated lift capacity is reached, pressure through the two lines denoted 4a and 5a will be disallowed regardless of other conditions.
  • Embodiments of the device as illustrated in figs 10, 11 and 12 provide the considerable advantage of requiring no boom level-sensing system for their correct operation. This represents a particularly welcome feature in crane hydraulics when one considers that the installation of level-sensing facilities, which must of course be applied direct to the boom, involves major complication of the system.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
EP19860830202 1985-11-27 1986-07-15 Hydraulische Lastbegrenzungsvorrichtung für hydraulische Krane Expired EP0224446B1 (de)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
IT4012885 1985-11-27
IT40128/85A IT1187219B (it) 1985-11-27 1985-11-27 Dispositivo idraulico per limitare il carico di gru azionate idraulicamente
IT4013585 1985-12-20
IT40135/85A IT1202291B (it) 1985-12-20 1985-12-20 Dispositivo idraulico perfezionato per limitare il carico di gru azionate idraulicamente
IT4001686 1986-02-28
IT40016/86A IT1189792B (it) 1986-02-28 1986-02-28 Dispositivo idraulico per limitare in modo indipendente della posizione angolare del braccio della gru il carico di gru azionate idraulicamente

Publications (3)

Publication Number Publication Date
EP0224446A2 true EP0224446A2 (de) 1987-06-03
EP0224446A3 EP0224446A3 (en) 1988-07-13
EP0224446B1 EP0224446B1 (de) 1991-04-24

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EP19860830202 Expired EP0224446B1 (de) 1985-11-27 1986-07-15 Hydraulische Lastbegrenzungsvorrichtung für hydraulische Krane

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EP (1) EP0224446B1 (de)
DE (1) DE3678905D1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5058752A (en) * 1990-03-20 1991-10-22 Simon-R.O. Corporation Boom overload warning and control system
US5597080A (en) * 1994-08-02 1997-01-28 Kranco Crane Services, Inc. Snag load protection system for a crane
US20170121941A1 (en) * 2014-06-18 2017-05-04 Cnh Industrial America Llc A Safety Hydraulic Circuit

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1531187A1 (de) * 1966-07-21 1969-07-31 Grove Mfg Co Sicherheitslastkontrollvorrichtung fuer Kraene
US3854593A (en) * 1971-12-24 1974-12-17 S Gross Overload switch-off device for hydraulic lifting or adjusting mechanisms connected in tandem, in particular for hydraulic loading and unloading cranes
GB2078197A (en) * 1980-06-04 1982-01-06 Hiab Foco Ab Load limiting device
DE3414183A1 (de) * 1984-04-14 1985-10-24 Robert Bosch Gmbh, 7000 Stuttgart Hydraulische ueberlastungsschutzvorrichtung fuer einen ladekran

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1531187A1 (de) * 1966-07-21 1969-07-31 Grove Mfg Co Sicherheitslastkontrollvorrichtung fuer Kraene
US3854593A (en) * 1971-12-24 1974-12-17 S Gross Overload switch-off device for hydraulic lifting or adjusting mechanisms connected in tandem, in particular for hydraulic loading and unloading cranes
GB2078197A (en) * 1980-06-04 1982-01-06 Hiab Foco Ab Load limiting device
DE3414183A1 (de) * 1984-04-14 1985-10-24 Robert Bosch Gmbh, 7000 Stuttgart Hydraulische ueberlastungsschutzvorrichtung fuer einen ladekran

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5058752A (en) * 1990-03-20 1991-10-22 Simon-R.O. Corporation Boom overload warning and control system
US5597080A (en) * 1994-08-02 1997-01-28 Kranco Crane Services, Inc. Snag load protection system for a crane
US20170121941A1 (en) * 2014-06-18 2017-05-04 Cnh Industrial America Llc A Safety Hydraulic Circuit
US10316495B2 (en) 2014-06-18 2019-06-11 Cnh Industrial America Llc Safety hydraulic circuit

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Publication number Publication date
DE3678905D1 (de) 1991-05-29
EP0224446A3 (en) 1988-07-13
EP0224446B1 (de) 1991-04-24

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