US2867047A - Multiple shell grab - Google Patents

Description

Jan. 6, 1959 H. ZIMMERMANN MULTIPLE SHELL GRAB 4 Sheets-Sheet 1 Filed June 11, 1956 I r t m INVENTOR. Hark/*2 Z z'mmel'malzlz,

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United States Patent O MULTIPLE SHELL GRAB Herbert Zimmermann, Dortmund, Germany, assignor to Hoesch Werke Aktiengesellsclraft, Dortmund, West Germany Application June 11, 1956, Serial No. 590,606

Claims priority, application West Germany December 19, 1955 15 Claims. (Cl. 37-182) This invention relates to a grab and more particularly to a grab of the multiple shell type which is adapted to be extended from the boom of a crane for lifting various objects and substances including earth, stones and the like.

For many years multiple shell grabs of this character have been faced with a problem where one or several of the shells of the grab encounters a relatively immovable object such as a large or rigidly fixed rock, for example, in the removal of earth. This problem is increased when the rock is larger than the grab. Such an encounter in previous devices has prevented the closing of the shells and did not permit the lifting of the material, including the rock that was causing the trouble. To overcome the problem it has previously been proposed to provide separate shells which are capable of independent movement, together with separate systems of cables and rollers for operating the individual shells. This arrangement has proved disadvantageous because of the great number of rollers, cables and parts required, which made the device cumbersome and subject to numerous failures.

It has also heretofore been proposed to provide devices of this character having link bars between the shell and the head member, said link bars being telescopic and having springs mounted inside them. Such link bars give and permit the shell to sink or move into the material, but since grabs are usually roughly handled and dropped onto the material to be picked up with a wide swing of the supporting boom and cable, it often happens that the link bars strike the material (such as scrap iron and the like), damaging the telescopic guides on the link bars. In another proposed device, the shells have been provided with slots permitting limited yielding movement of any individual shell relative to the others if, when closing, it should strike an immovable object. Such slots, however, have a tendency to become clogged with the material that is being handled and this clogging hinders the proper functioning of the grab.

It is accordingly an object of this invention to overcome the disadvantages just referred to.

It is another object of this invention to provide an improved, non-clogging means for permitting independent movement of each grab shell for allowing a shell to lag behind the other shells upon encountering a strong resistance.

Another object of this invention is to provide means for cushioning the shock to which parts of the mechanism are subjected when a shell encounters a rigid object.

It is another object .to provide an improved means for allowing limited lateral movement of the shell at an angle to the plane of its swinging movement.

It is a further object of this invention to provide a multiple shell grab of the type just referred to wherein the shells are pivotally connected to link bars and where- .in the pivotal connections are guarded and protected against blows, clogging and other damage. Another ob-' cry of the head member.

ject is to provide a grab of this type having a head member of strong construction and yet of light weight so that a maximum pay load can be handled.

Still another object is to provide a multiple shell grab having shells that are operated frequently and that strike the material to be handled with considerable force and yet do not subject the grab to excessive impact forces. It is another object to provide a device of this type having a strong link bar connection between the shells and the mechanism operating the shells.

Other objects and advantages of the invention will further become apparent hereinafter and in the drawings in which:

Fig. 1 represents a top plan view of a multiple shell grab embodying features of this invention;

Fig. 2 represents a vertical sectional view of the grab shown in Fig. 1 taken as indicated by the lines and arrows II-II which apear in Fig. 1, with certain parts being broken away and shown in section in order to illustrate important details;

Fig. 3 represents a sectional view taken as indicated by the lines and arrows IIII'II which appear in Fig. 2;

Fig. 4 represents a view in fractional elevation of one of the link bars that connects one of the shells to the head member;

Figs. 5 and 6 represent sectional views taken as indicated by the lines and arrows VV and VI-VI which appear in Fig. 2;

Fig. 7 represents a perspective view of a modified form of one of the link bars;

Fig. 8 represents a view in fractional elevation showing the modified link bar of Fig. 7 connected to the head member;

Fig. 9 represents a view in section taken as indicated by the lines and arrows IX-lX which appear in Fig. 8;

Figs. 10 and 11 represent modified forms of the apertures of the ears of the head member; and

Fig. 12 represents a fractional view of One of the head member ears with a resilient cushion disposed therein.

Although specific terms are used in the following description for clarity, these terms are intended to refer only to the structure shown in the drawings and are not intended to limit the scope of the invention.

Turning now to the specific form of the invention selected for illustration in the drawings, thenumber 20 designates a grab head which is hell shaped and which is suspended from above by a rope orcable 21.Cable 21 is suspended from the boom of a crane or from similar apparatus (not shown) which operates to raise and lower, and otherwise position the grab. Suspended fromhead 20 by means of another rope orcable 22 is abase 23, which is of circular shape and which has pivotally mounted about its periphery in star fashion a plurality of grab claws orshells 24. A plurality ofrigid link bars 25 are pivotally connected between theshells 24 andhead member 20 at equally spaced points around the periph- The upper ends oflink bars 25 are slidably pivoted to outwardly extendingears 26 which are aifixed to the outer periphery ofhead member 20. Cable 22 is trained around a series ofpulleys 27 carried onhead member 20, and another series ofpulleys 28 carried on thebase 23, which allow the base to be raised and lowered relative to the head member. When power is applied tocable 22 to pull it in an upward direction, thebase 23 is raised toward thehead 20 and thelink bars 25 coact with the base and head to swing theshells 24 about their pivoted connection with the base to their closed position. Whencable 22 is released from tension, the weight of thebase 23 together with the weight of theshells 24 and thelink bars 25 is -suflicient to swing open theshells 24 by gravity action Thehead member 20 is bell or dome shaped, having aperipheral flange 31. Welded to theside walls 32 ofhead 20 are a number ofears 26 each of which has anaperture 33 formed therein in which is positioned a barrel shaped transverse shaft 34 (Pig; Apin 35, having aslotted head 36 and a threadedend 37 on which is turned anut 38, is centrally located withinshaft 34 and serves to connectaperture 33 with thehollow arms 41, 42 oflink bar 25.Aperture 33 is sufficiently large by comparison withshaft 34 to provide clearance that permits the longitudinal axis of the sleeve to rock within the aperture.Ears 26 are provided withsidewalls 43 that are angled at 44. Aresilient pad 39 is aflixed in the upper extremity of the inner wall ofaperture 33 of each ear 26 (Fig. 12). Figs. and 11 show modifications in the shape of the ear apertures, a substantially oval shapedaperture 33a and a kidney shapedaperture 33b. Immediately belowears 26,resilient pads 40 are securely but removably attached towall 32.

Eachlink bar 25 includes a hollow substantially square shapedmiddle portion 45 and anupper fork section 46, as well as alower fork section 47 formed by thearms 48, 49. The arms of thelower fork section 47 are reinforced by a plate 50 (Figs. 2 and 7), which is welded or otherwise secured to thesection 47 at the juncture of thearms 48, 49.Plate 50 is of trapezoidal configuration and has aweb 51 which extends diagonally from one side of thebar 25 to the other, within the fork formed by thearms 48, 49.Reinforcement straps 54 are welded between theupper arms 41, 42 andlower arms 48, 49.Inner holes 56 are provided in the arms to admit the pins, andholes 57 are provided in the outer surfaces of the arms for allowing the admission of a screw driver or other tool to rotate the pin into its tightened position. The modifiedlink bar 25a shown in Fig. 7 is provided withslots 58 which coact with thecircular holes 61 provided in thecar 26 illustrated in Fig. 9, for allowing longitudinal n ovement oflink bar 25a with respect to head member 2 It will be noted that the arms of thelink bars 25 and 25a are substantially channel shaped and haveplates 60 welded to the edges of the flanges of the arms to form a strong, rigid structure.

Thebase 23 comprises a circularupper plate 62 and a circularlower plate 63 havingradial slots 64 formed therein to permit swinging ofshells 24. Upper andlower plates 62 and 63 are rigidly joined to each other byvertical webs 65 which are arranged in pairs at equally spaced points around the peripheral edge of the base at the edges ofslots 64. Theshells 24 are pivotally connected to thebase member 23 between thewebs 65 which haveholes 66 that receive barrel shapedpivot shafts 67 on which a shell is hung.

Eachgrab shell 24 is formed of acurved metal plate 68, to the convex face of which is welded or otherwise secured a centralperpendicular saddle plate 71 havingside plates 72 affixed to thecurved plate 68. The end ofsaddle plate 71 is formed into astop flange 73 that is arranged to coact with stop lugs 74 mounted onupper plate 62 ofbase member 23, to limit the upward swing ofshells 24. A resilient pad 75 is removably attached to flange 73 to cushion the shock of contact betweenflange 73 and lugs 74.

The central upper portion ofeachsaddle plate 71 is apertured at 76 (Fig. 6), and a barrel shaped,transverse pivot shaft 77 extends throughaperture 76 to pivot theshell 24 to linkbar 25. Bothpivot shaft 67 connectingshell 24 withbase member 23, andpivot shaft 77 connectingshell 24 withlink bar 25 are loosely connected within their associated apertures to provide sufficient clearance to allow limited lateral movement of the connected parts, permittingshell 24 to rock laterally with respect to the plane of the shells swinging movement. Reinforcingplates 78 are welded to saddleplate 71adjacent t e aperture 76.

In operation the grab is suspended oncable 21 withcable 22 relaxed and theshells 24 open as in Fig. 2. The grab is lowered on top of the material to be lifted as shown in Fig. 2, and thecable 22 is pulled to close thegrab shells 24. The pulling oncable 22causes base member 23 andhead member 20 to move toward each other. This relative movement of the head and base members acts upon link bars 25 to force theshells 24 to rotate upon theirpivot shaft 67. Upon encountering resistance eachshell 24 is allowed, by the loose pivot connections atshafts 67, 77 and 34 and by the barrel shape of the pivot shafts, to rock independently of each other and to follow the line of least resistance in scooping up the material to be excavated or handled. Inclosing grab shells 24,pads 40 cushion the shock and also prevent rocking of the closed shells. Should one or several of theshells 24 encounter a resisting force that impedes its progress, the slotted arrangement of thecars 26 as typified in Fig. 2, or the slottedarrangement 58 of theupper fork 46 as shown in Figs. '7 and 8, allow such a shell to lag behind the others in closing. It will be noted that the outer surface ofarms 41, 42, 48, 49 protect the pivot mechanism from blows, damage and from clogging, and that reinforcingstraps 54 and reinforcingplate 50 provide added strength to reinforce link bars 25.Straps 54 andplate 50 are positioned to minimize clogging and the pouring of material through the space between the forked arms. After theshells 24 have closed the grab is lifted by means ofcable 21 and swung to position for emptying, whereupon the tension oncable 22 is released and the weight of the load plus the weight of thebase member 23,shells 24, and link bars 25 act to movebase member 23 away fro-m head member 20 andopen shells 24 to release the load.

On opening theshells 24, resilient pad 75 onstop flange 73 ofsaddle plate 71 contacts lug 74 ofbase member 23 to cushion the strain of impact.

The bell or dome shape of thehead member 20 is of particular advantage since it combines great strength with light weight and with the head member of light weight the pay load is proportionately increased. The location adjacent the head member of the slots that allow a shell to lag behind the others has several advantages, the slots are less likely to become clogged or receive blows and the weight of the link bars and the shells are added to the weight of the base to aid in moving the base away from the head to open the shells. The pivot connections include a barrel shaped shaft positioned within apertures of sutiicient clearance for allowing a rocking action to permit the shells to follow the line of least resistance in their downward swing, and the hollow double forked arms protect the pivot components against blows while the resilient pads cushion the stop limits of the mechanism.

It is to be understood that the form of the invention herein shown and described is to be taken as a preferred embodiment. Various changes may be made in the shape, size and arrangement of parts. Equivalent elements may be substituted for those described herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of other features, all without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, I claim:

1. A multiple shell grab comprising a head member, a base member normally positioned below the head member, means connected to the head and base members for moving said head and base members toward each other against the action of gravity, a plurality of grab shells pivotally connected to said base member in star fashion with capacity for swinging movement to open and close said shells, substantially rigid means pivotally connected to said head member and pivotally connected to said shells for swinging said shells in response to the movement-between said head and base members, and connecting means including a lost motion connection adjacent to said head member between said rigid means and said head member providing for movement of said rigid means in a direction generally extending between said head and base members to provide for a shell lagging behind the other shells in closing upon encountering a strong resistance.

-2. The multiple shell grab defined in claim 1, wherein said head member is hell shaped.

3. The multiple shell grab defined in claim 1, wherein resilient stop means are interposed between said base l member and the shells for limiting the swinging movement of the shells.

4. The multiple shell grab defined in claim 3, wherein said stop means includes a resilient pad mounted on a flange of the shell near its pivotal connection to said base member, and a lug mounted on said base member providing for engagement with said resilient pad when said shells are opened.

5. The multiple shell grab defined in claim 1, wherein said substantially rigid means includes a rigid bar with a pair of arms forming a forked upper end, and said lost motion connection includes a slot formed in the arms of said bar.

6. The multiple shell grab defined in claim 1, wherein said lost motion connection includes an ear rigidly affixed to said head member, said ear having an elongated aperture formed therein, said substantially rigid means being connected into said aperture.

7. The multiple shell grab defined in claim 6, wherein said aperture is kidney shaped.

8. The multiple shell grab defined in claim 6, wherein said aperture is substantially oval shaped.

9. The multiple shell grab defined in claim 6, said aperture having resilient means afiixed at the extremity of its inner wall for cushioning shock.

10. The multiple shell grab defined in claim 6, wherein the side walls of said ears are angled.

11. The multiple shell grab defined in claim 6, wherein resilient stop means are aflixed inside the elongated aperture of said ear.

12. A multiple shell grab comprising a head member, a base member normally positioned below the head member, means connected to the head and base member for moving said head and base member toward each other against the action of gravity, a plurality of grab shells pivotally connected to said base member in star fashion with capacity for swinging movement to open and close said shells, shell moving means including a substantially rigid link bar for moving said shells in response to the movement between said head and base members, and connecting means including a lost motion connection adjacent to said head member between said link bar and said head member providing for movement of said link bar in a direction generally extending between said head and base members to provide for a shell lagging behind the other shells in closing upon encountering a strong resistance, said shell moving means including a rigid link bar having a substantially square shaped middle portion and arms forming upper and lower forked end portions, a barrel shaped transverse shaft extending between the arms of said forked end portions, said shaft of the upper forked end portion being loosely pivotally connected to said connecting means, and said shaft of the lower forked end portion being loosely pivotally connected to one of said shells whereby said shells have capacity for limited lateral movement at an angle to the plane of their swinging movement.

13. The multiple shell grab defined in claim 12, wherein said arms are hollow and the ends of the transverse shaft extending between said arms are recessed within the interior of said arms whereby to protect said shaft ends against blows and damage.

14. The multiple shell grab defined in claim 12, where ally diverging portion of said arms that form said lower forked end portion.

15. The multiple shell grab comprising a head member, a base member normally positioned below the head member, pulley means connected to said head and base members and a system of cables trained around said pulley means for moving said head and base members toward each'other against theaction of gravity, a plurality of grab shells pivotally connected to said base member instar fashion with capacity for swinging movement to open and close said shells, substantially rigid means pivotally connected to said head member and pivotally connected to said shells for swinging said shells in response to the movement between said head and base members, and connecting means including a lost motion connection adjacent to said head member between said rigid means and said head member providing for movement of said rigid means in a direction generally extending between said head'and base members to provide a shell lagging behind the other shells in closing upon encountering a strong resistance, and means connected to said rigid means, to said connecting means and to said shells providing for limited lateral movement of said shells at an angle to the plane of their swinging movement.

References Cited in the file of this patent UNITED STATES PATENTS 254,824 'Johnson Mar. 14, 1882 271,538 Stone Jan. 30, 1883 1,935,898 Zimmerman et a1. Nov. 21, 1933 FOREIGN PATENTS 347,093 Germany Jan. 12, 1922 466,546 Germany Oct. 9, 1928 515,809 Great Britain Dec. 14, 1939 456,384 Italy Apr. 1, 1950

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