US3207548A - Locking device for the jaws of a mechanical grab - Google Patents

Locking device for the jaws of a mechanical grab Download PDF

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Publication number
US3207548A
US3207548A US214671A US21467162A US3207548A US 3207548 A US3207548 A US 3207548A US 214671 A US214671 A US 214671A US 21467162 A US21467162 A US 21467162A US 3207548 A US3207548 A US 3207548A
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United States
Prior art keywords
detent
jaws
grab
pawl
load
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Expired - Lifetime
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US214671A
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English (en)
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Moskopf Peter Franziskus
Mengden Heinrich Valentin
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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
    • B66C1/00—Load-engaging elements or devices attached to lifting or lowering gear of cranes or adapted for connection therewith for transmitting lifting forces to articles or groups of articles
    • B66C1/10—Load-engaging elements or devices attached to lifting or lowering gear of cranes or adapted for connection therewith for transmitting lifting forces to articles or groups of articles by mechanical means
    • B66C1/42—Gripping members engaging only the external or internal surfaces of the articles
    • B66C1/422—Gripping members engaging only the external or internal surfaces of the articles actuated by lifting force

Definitions

  • This invention relates to mechanical grabs of the suspended bucket type such as are used for the picking up, transporting, and discharge of solid materials. It is particularly, although not exclusively, concerned with grabs designed for large flat articles whose upper surface is approximately horizontal; with such grabs it is desirable, in order to save labor, to provide means which will automatically lock the grab after the articles have been gripped and release them when they have been set down.
  • the invention presents a solution for this problem by linking to a jaw of the grab a feeler in the form of, for example, a cranked lever adapted to be moved by the load and whose one end actuates a pivotally mounted detent which, when the load is released, engages a projection or trip member on the other jaw of the grab so as to maintain the jaws in the open position.
  • each jaw is constituted by a generally bell-crank shaped frame having at least two parallel side arms and at least two parallel bars joining the arms, the one extremity of one frame being pivotally connected to the angle of the other.
  • the said detent is actuated by a pawl formed at its free end as a hook engageable with the said feeler.
  • a further object of the invention is to provide that the said detent is free to pivot on the same jaw as that to which the said feeler is connected, and the said detent may be biased towards its operative position by a tension spring connected to the said pawl.
  • the free end of the pawl may be connected by another tension spring to the other jaw of the grab which carries the said trip plate or detent-engaging projection.
  • the feeler may in certain cases be desirable to shape the pawlengaging end of the feeler as a fork which embraces the pawl.
  • the load to be picked up is sensitive to shock or impacte.g. slabs of green concrete-it may be damaged by the impact of the feeler if the co-operation of the several parts of the locking device is such that the grab jaws can close quickly upon making contact with the load. Furthermore,-the impact of the feeler itself on rapid lowering of the grab could subject the load to considerable shock and might cause undesirable damage.
  • the said pawl is elastically linked to the said detent, as by a tension spring so as to permit the feeler to yield on first impact with the load.
  • the detent may itself be spring-loaded to the position of engagement with the said trip member.
  • the end of the pawl which is engaged by the said feeler may be arranged to rest on a fixed abutment when the grab arms are locked, said abutment disengaging the pawl from the said feeler when the grab jaws fall free.
  • FIGURE 1 is a perspective View of a conventional form of grab consisting of two pairs of arms and parallel load-gripping bars;
  • FIGURE 2 is a plan view of the grab of FIGURE 1 but showing a locking device according to the invention
  • FIGURES 3 to 5 are similar side elevations showing the locking device according to the invention in three different positions;
  • FIGURE 6 is a plan view of a modified locking device according to the invention.
  • FIGURE 7 is a fragmentary section on the line VII VII of FIGURE 6 showing the positions of the parts when the grab is in the open position, and
  • FIGURE 8 is a section similar to FIGURE 7 showing the positions of the parts when the grab has already picked up the load.
  • the conventional grab illustrated in FIGURE 1 consists of two pairs of cranked frames 1 and 2 constituting the jaws and which can be suspended in any desired manner, as from a traveling crane, truck derrick, or simply on a cable 4 anchored to a rod 3.
  • the arrow 5 shows the lifting and lowering motion of the suspension which controls the entire grab.
  • the two side arms 9, 11 and 10, 12, respectively of each jaw 1, 2 are connected by respective bars 6 which, in the position shown in FIGURE 1, have just gripped the load 8. Any downward movement of the suspending tackle 4 causes the jaw bars 6 to move in the direction of the arrows 7 and release the load 8.
  • the grab illustrated is suitable for gripping a pile of, concrete slabs or any similar articles which have a fairly fiat horizontal upper surface; other examples are railway sleepers, curb stones, timber, piles of planks and the like.
  • Each pair of jaw frames 1, 2 consists of two L-shaped side arms 9, 14) or 11, 12.
  • the arms 9 and 11 are firmly connected by ties 13, 14, and the arms 10 and 12 by similar ties 15, 16.
  • the tie 17 not only connects the arms 10 and 12, but also forms the pivot for the arms 9 and 11, so that the jaws 1, 2 can pivot on each other when the grab is raised or lowered.
  • FIGURE 2 shows the locking device which is omitted from FIGURE 1.
  • An additional tubular tie 18 is shown interconnecting the side arms 9 and 11; this serves as a carrier for the detent 29 described below.
  • To the tubular tie 14 are welded two brackets 20 and 21 which carry a pivotal yoke tube 22.
  • a pair of levers 23 extend from this yoke tube near its ends and carry feeler plates 24 at their free ends.
  • Each feeler plate 24 is preferably made of sheet metal or plastic and is adapted to make direct contact with the upper surfaces of the load.
  • To the yoke tube 22 is secured, at an obtuse angle to the levers 23 (see FIGURES 3 to a fork 25, which is thus rigid with the feeler plate 24.
  • the fork 25 is mounted by a short pillar 26 on the yoke tube 22.
  • the latter also carries, as can be seen in FIGURES 3 to 5, a projecting stop which limits the downward movement of the feeler plate 24.
  • the additional tubular tie 18 between the arms 9 and 11 carries two brackets 27, 28 supporting a triangular detent 29 mounted on a pivot pin 30 and coupled by a stud 31 to a pawl 32; the later has at its free end a notch or shoulder 33 or equivalent releasable interengagement means which, in the fully open position of the jaws 1, 2, can engage the fork 25.
  • the detent 29 has a tail stop 29a which limits the counter-clockwise movement of the detent, as seen in FIGURES 3 t
  • a small anchor plate 34 is welded radially to the tie 18 and serves as an anchorage for one end of a tension spring 35, whose other end is attached to the pawl 32 at a point 36.
  • the operation of the locking device is as follows:
  • the grab comprises two L-shaped grab jaws 1, 2 respectively which are connected by a pivot rod 17.
  • Each jaw has a pair of bellcrank side arms, only one of each pair being shown at 9, 10 respectively in FIGURES 7 and 8.
  • the several pairs of side arms are inter-connected by respective tubular frames, the tubes 13 and 14 for instance connecting the side arm 9 to a corresponding arm (not shown) while the tube 16 connects the side arm 10 to corresponding arm (also not shown).
  • Other such connecting tubes perpendicular to the plane of section in FIGURES 7 and 8 are also provided as necessary.
  • a connecting tube 44 extending perpendicularly to the plane of section in FIGURES 7 and 8.
  • the grab bars (not shown) aflixed to the free ends of the grab arms 9 and 10 likewise extend perpendicularly to the plane of section.
  • a feeler in the form of a two-armed bellcrank lever 23 is provided with a feeler plate 24 which makes contact directly with the load material picked up by the grab, and has a pivoted yoke tube 22 rotatably mounted in brackets 20, 21.
  • a fork 25 fixed to the yoke tube 22 will therefore be deflected in the direction of the arrow 46 when the feeler plate 24 moves in the direction of the arrow 47 after having made contact with the load.
  • the fork 25 engages a notch 33 in a pawl 32 which is thus pulled to the left in the drawings when the fork is deflected to the left.
  • the forward end 32a of the pawl slidably rests on an abutment member 45 afiixed to the tube 13.
  • the abutment member 45 consists of a slanting plate with an extension 45' upon which the forward end 32a of the pawl 32 actually rests.
  • the pawl 32 is fastened to a link 48 mounted on a pivot 49.
  • This pivot 49 is at the end of a bar 50 fixed to the tube 16.
  • a tension spring 35 Attached to the free end of the link 48 is a tension spring 35.
  • the other end of this spring is fastened to a detent 29, which is pivotally mounted on a pin 30 in a fork-shaped bracket 28 and is associated with another tension spring 51 of which one end, as shown in FIG- URES 7 and 8, is attached to the detent 29 approximately level with tension spring 35, while its other end is anchored on a lug 52 which is fixed to the bracet 28.
  • the lug 52 is non-rotatably fixed to the bracket.
  • the coupling of the feeler 23 to the detent 29 by means of a spring 35 permits the initial contact pressure of the feeler plate 24 on the load to be kept to a minimum.
  • the full pressure required to release the detent 29 from engagement with the trip plate 41 is built up gradually.
  • articulated jaws 1, 2 adapted to grip loads automatically on hoisting can be substituted if desired.
  • the invention is not limited to the specific shapes and configurations of individual components of the jaw locking mechanism as particularly described above, save insofar as said shapes or configurations are essential to the functioning of the parts as required by the appended claims.
  • a suspended grab comprising a pair of pivoted jaws; means for raising and lowering the jaws; a detent pivoted on one jaw; a trip member engageable by said detent on the other jaw so as to maintain said jaws in the open position; a pawl linked at one end to said detent. and releasable inter-engagement means at the other end of the pawl,
  • a movable feeler releasably engageable at one end with said means on said pawl and adapted at the other end to make contact with a load as the open jaws are lowered thereonto and release said detent from engagement wtih said trip member.
  • a suspended grab comprising a pair of pivoted jaws; means for raising and lowering the jaws; a detent pivoted on one jaw; a trip member engageable by said detent on the other jaw so as to maintain said jaws in the open position; a pawl pivotally connected at one end to said detent and releasable inter-engagement means at the other end of the pawl, and a movable feeler releasably engageable at one end with said means on said pawl and adapted at the other end to make contact with a load as the open jaws are lowered thereonto and release said detent from engagement with said trip member.
  • a suspended grab comprising a pair of pivoted jaws; means for raising and lowering the jaws; a detent pivoted on one jaw; a trip member engageable by said detent on the other jaw so as to maintain said jaws in the open posi tion; a pawl elastically linked at one end to said detent and releasable inter-engagement means at the other end of the pawl, and a movable feeler releasably engageable at one end wtih said means on said pawl and adapted at the other end to make contact with a load as the open jaws are lowered thereonto and release said detent from engagement with said trip member.
  • a suspended grab comprising a pair of pivoted jaws; means for raising and lowering the jaws; a detent pivoted on one jaw; a trip member engageable by said detent on the other jaw so as to maintain said jaws in the open position; a load-contacting feeler pivotally mounted on said one jaw; a pawl releasably engageable by said feeler; a pivotal mounting for said pawl on said one jaw; and a tension spring inter-connecting said pawl and said detent for progressively applying a disengaging force from said feeler to said detent.
  • a grab comprising a pair of pivotally inter-connected load-gripping jaws, each jaw comprising at least one pair of rigidly spaced parallel cranked side arms; a load-contacting feeler pivoted on one of said jaws; a detent also pivoted on the same jaw; a trip member fixed on the other of the jaws and engageable by said detent in the open position of said jaws; a pawl releasably engageable by said feeler, and means for coupling said pawl to said detent whereby deflection of said feeler on contacting a load while the jaws are in the open position causes disengagement of said detent from said trip member.
  • a grab comprising a pair of pivotally interconnected load-gripping jaws, each jaw comprising at least one pair of rigidly spaced parallel cranked side arms; a load-contacting feeler pivoted on one of said jaws; a detent also pivoted on the same jaw; a trip member fixed on the other of the jaws and engageable by said detent in the open position of said jaws; a pawl releasably engageable by said feeler, and an elastic connection between said pawl and said detent for progressively applying a force to said detent to cause it to disengage said trip member as said feeler is deflected by contact with a load.
  • a grab comprising a pair of pivotally interconnected load-gripping jaws, each jaw comprising at least one pair of rigidly spaced parallel cranked side arms; a load-contacting feeler pivoted on one of said jaws; a detent also pivoted on the same jaw; a trip member fixed on the other of the jaws and engageable by said detent in the open position of said jaws; a pawl pivotally connected at one end to said detent and means at the other end for releasable engagement with said feeler whereby deflection of said feeler on contacting a load while the jaws are in the open position causes disengagement of said detent from said trip member.
  • a grab comprising two pairs of laterally spaced rigidly interconnected cranked side arms constituting loadgripping jaws, each arm having limbs of unequal length and the extremities of the longer limbs of one pair of side arms being pivotally connected at the apex of the angles of the other pair of side arms; a rigid load-gripping member interconnecting the extremities of the shorter arms of each pair; a suspension member connected to the extremities of the longer arms of said other pair of side arms; and releasable locking means for releasably holding said jaws in the open position in which the said longer limbs lie substantially horizontally over a load to be gripped while the shorter limbs depend to embrace the load, said locking means comprising a detent pivotally mounted on one jaw approximately centrally of the longer limbs of the side arms thereof; a trip member fixed on the other jaw for engagement by said detent in the open position of said jaws; a pawl coupled to said detent and lying substantially horizontally when said detent is in engagement with said trip member
  • a grab according to claim 11 comprising a bracket fixed on the jaws carrying said detent; said pawl being pivotally connected to said bracket, and a tension spring coupling said pawl to said detent for applying a trip disengaging force thereto.
  • a suspension grab including a pair of pivoted arms, a locking device adapted for locking the arms in an open position, said device comprising: a feeler constituted by a cranked lever adapted for contacting a load which is to be engaged by the arms of the grab, a pawl supported for pivotal movement on one of the arms, said lever having an end which is engageable with said pawl with the arms in an open position, a detent supported for pivotal movement on said one arm, means connecting said pawl and said detent to pivotally move the latter from a first to a second position as the feeler contacts the load to be engaged by the arms of the grab, and a trip member secured to the other of the arms and engageable by the detent with the latter in said first position to keep said arms locked in the open position and being free of said detent with the feeler in contact with the load which is to be engaged and the detent in the second position thereof.
  • a suspension grab as claimed in claim 14 having a first spring with a first end secured on one of said arms and a second end connected to the pawl, a second spring having a first end secured on the other of said arms and a second end connected to said pawl, said pawl being disengaged from the feeler by one of the springs, the detent being urged to the first position thereof by the other of said springs.
  • a suspension grab as claimed in claim 18 comprising a second spring having one end fixedly secured on the arm with which the detent is supported for pivotal movement, the second spring having another end secured to the detent for urging the same to the first position thereof.
  • a suspension grab as claimed in claim 14 comprising an abutment supported on the arm with respect to which the feeler is supported for pivotal movement, said 5 pawl having, a free end supportedon the abutment and being lifted by the abutment as the load is engaged by the grab to be freed from the feeler.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Load-Engaging Elements For Cranes (AREA)
US214671A 1961-11-06 1962-08-03 Locking device for the jaws of a mechanical grab Expired - Lifetime US3207548A (en)

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Application Number Priority Date Filing Date Title
AT834961A AT230061B (de) 1961-11-06 1961-11-06 Sperrvorrichtung zum Verriegeln eines von einer Hängevorrichtung lotrecht herabhängenden Greifers in Offenstellung

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3703309A (en) * 1970-06-23 1972-11-21 Jacob H Mosterd Automatically discharging gripper device
FR2512428A2 (fr) * 1981-09-08 1983-03-11 Bunel Bernard Pince de levage pour produits divers, tels que des sacs de ciment, des tubes... reunis en tas ou en gerbe par une enveloppe
WO1985001720A1 (en) * 1983-10-13 1985-04-25 Eriksson Sven Goeran A device for lifting and handling objects
FR2784086A1 (fr) * 1998-10-05 2000-04-07 Michel Massin Dispositif de prehenseur auto-serrant pour la manutention de charges
US6820907B1 (en) * 2001-09-12 2004-11-23 Scott D. Haynes Multi-unit concrete block tongs
US20070014654A1 (en) * 2005-07-13 2007-01-18 Haverfield Forrest A Pallet clamping device
CN112573353A (zh) * 2020-12-31 2021-03-30 青岛港国际股份有限公司 一种空轨动车吊具及控制系统、控制方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US900889A (en) * 1908-02-17 1908-10-13 John Schuster Hog-catcher.

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US900889A (en) * 1908-02-17 1908-10-13 John Schuster Hog-catcher.

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3703309A (en) * 1970-06-23 1972-11-21 Jacob H Mosterd Automatically discharging gripper device
FR2512428A2 (fr) * 1981-09-08 1983-03-11 Bunel Bernard Pince de levage pour produits divers, tels que des sacs de ciment, des tubes... reunis en tas ou en gerbe par une enveloppe
WO1985001720A1 (en) * 1983-10-13 1985-04-25 Eriksson Sven Goeran A device for lifting and handling objects
US4637645A (en) * 1983-10-13 1987-01-20 Eriksson Sven Goeran Device for lifting and handling objects
FR2784086A1 (fr) * 1998-10-05 2000-04-07 Michel Massin Dispositif de prehenseur auto-serrant pour la manutention de charges
US6820907B1 (en) * 2001-09-12 2004-11-23 Scott D. Haynes Multi-unit concrete block tongs
US20070014654A1 (en) * 2005-07-13 2007-01-18 Haverfield Forrest A Pallet clamping device
US7544037B2 (en) 2005-07-13 2009-06-09 Crown Equipment Corporation Pallet clamping device
CN112573353A (zh) * 2020-12-31 2021-03-30 青岛港国际股份有限公司 一种空轨动车吊具及控制系统、控制方法
CN112573353B (zh) * 2020-12-31 2022-05-24 青岛港国际股份有限公司 一种空轨动车吊具及控制系统、控制方法

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