Jack-actuated crane tongs

Abstract

The legs of tongs are pivotally mounted between plates supported both to rotate about a vertical axis for turning the tongs, and to swing about a horizontal axis relative to a crane boom to enable the tongs to be disposed in depending position irrespective of the angle of the crane boom. The tongs legs can be swung toward and away from each other by toggle linkage actuated by an upright jack such as a hydraulic jack or a non-rotative screw reciprocated by a nut power-rotated by a hydraulic motor driving the nut through a chain-and-sprocket drive or a gear.

Parent Case Text

This application is a continuation-in-part of application Ser. No. 175,467 on Screw-Actuated Crane Tongs, filed Aug. 27, 1971, now abandoned.

Description

A principal object of the invention is to provide power-actuated crane tongs which can be driven positively to move the legs of the tongs into a predetermined spread position in which they will remain without the continuing application of power to them.

A further object is to provide power-operated tongs which can be operated by screw means mounted adjacent to the tongs and connected to a source of power such as by wires or preferably by conduits through which fluid under pressure is supplied.

Another object is to provide such power-operated tongs which are mounted both for swiveling and for swinging relative to a crane boom, by which the tongs are supported.

It is also an object to be able to use the same power means to open and close the tongs and to swivel the tongs relative to the crane boom.

A further object is to provide strong and effective power means for swinging the tongs legs relatively and which is compact and reliable in operation.

FIG. 1 is a top perspective of tongs according to the present invention mounted on the end of a crane boom. FIG. 2 is a side elevation of the tongs mounted on the end of a crane boom on an enlarged scale, parts being broken away.

FIG. 3 is a central vertical section through the root portions of the tongs legs and the mounting structure, parts being broken away, and showing the tongs legs in spread relationship; and FIG. 4 is a similar view showing the tongs legs in fully contracted relationship.

FIG. 5 is a horizontal section through the mounting structure for the crane tongs, taken on line 5--5 of FIG. 3.

FIG. 6 is a central vertical section taken on line 6--6 of FIG. 8 through the root portions of the tongs legs and the mounting structure showing an alternative type of tongs mechanism, the tongs legs being in spread relationship. FIG. 7 is a similar view with the tongs legs in fully contracted relationship.

FIG. 8 is a horizontal section through the mounting structure for the crane tongs taken on line 8--8 of FIG. 6.

It has been customary to mount tongs on a crane boom either in a very flexible fashion, such as on the end of a cable depending from the crane boom or in a rigid fashion, such that the tongs cannot swivel relative to the crane boom if power means is provided to close the tongs. In accordance with the present invention, the legs 1a and 1b of the tongs are supported from the crane boom 2 so that, not only can the tongs legs be opened and closed positively under power, but the tongs can be swiveled under power relative to the crane boom and can swing relative to the crane boom. By such swinging, the tongs will always be able to return to depending relationship relative to the crane boom, irrespective of the angle of the crane boom, when the load has been removed from the tongs.

The tongs mount 3 is supported by trunnions 4 projecting outward from its opposite sides, which trunnions are mounted in bearings 5 in the bifurcations of the crane boom 2 so that the tongs can swing relative to the boom in whatever swung position the boom may be. The tongs will therefore always tend to return to depending position in which their legs 1a and 1b are disposed substantially in an upright plane. The tongs mount 3 has a large central aperture 6 for receiving the swivel support for the tongs.

The root portions of the tongs legs are inserted between parallel vertical plates 7, as shown in FIG. 2, the upper edges of which are welded or otherwise permanently attached to a turntable 8, as shown in FIG. 3. The margin of such turntable is fitted rotatively within a groove 9 in the tongs mount 3 opening into central aperture 6. The turntable will thus support the weight of the tongs legs and any load gripped by them for swiveling about a substantially upright axis.

The tongs legs 1a and 1b are mounted for relative vertical swinging about horizontal pivots 10a and 10b, respectively, which extend through the root portions of the respective tongs legs and the parallel plates 7 on opposite sides of them. FIGS. 3 and 4 shown such pivots located a short distance below the trunnions 4. As shown in FIG. 5, the tongs leg 1a is slightly narrower than the tongs leg 1b and spacing washers 11 are mounted on the pivot rod 10a between the root portion of the leg 1a and the side plates 7 to maintain the parts of the tongs centered between such plates.

The actuating mechanism for swinging the tongs legs relatively toward and away from each other includes bars or links 12a and 12b of a toggle joint having their remote ends connected respectively to the leg 1a and the leg 1b of the tongs by pivots 13a and 13b, respectively, located below the pivots 10a and 10b. The adjacent ends of the toggle joint bars 12a and 12b are disposed in overlapping relationship, as shown in FIGS. 3 and 5, and are connected together by the common pivot pin 14, the opposite ends of which are received in and guided for elevational movement by upright slots 15 in the side plates 7 of the tongs mount.

The legs 1a ahd 1b of the tongs are spread apart by forcing the toggle joint pivot 14 downward in slots 15 to move the toggle joint bars 12a and 12b toward alignment. Alternatively the tongs legs are swung toward each other, such as to the fully closed position shown in FIG. 4, or to any intermediate clamping position, by elevating the toggle joint pivot 14 along slots 15 to pull the toggle joint pivots 13a and 13b toward each other. Such elevational movement of the toggle joint pivot is effected by exerting a raising or lowering force on the collar 16 encircling the central portion of the toggle joint pivot 14 with a jack. A jack spindle 17 connected rigidly to the collar 16 and projecting radially from it and from the toggle joint pivot 14 extends upwardly from the collar, as shown in FIGS. 3 and 4.

Elevational lengthwise non-rotative movement of the spindle 17 to effect relative swinging of the tongs legs 1a and 1b is accomplished by making the spindle a screw and rotating relative to it a nut 18 extending through a central aperture 19 in the turntable 8 of the tongs mounting structure. This nut is supported by an upper shoulder 20 engaging a thrust bearing 21 interposed between such shoulder and the depressed, inner margin of the turntable 8 encircling the aperture 19. The nut is rotated to effect elevational longitudinal movement of the screw 17 by rotation of a sprocket 22 integral with the nut 18, which is rotated by a roller chain 23, although the nut could be turned by suitable gearing.

As shown best in FIG. 2, the roller chain is driven by a motor 24, preferably of the hydraulic type, although it may be an electric motor, or could be driven by a belt or cable drive. This motor is mounted on a support 25 offset from the sprocket 22 and screw 17 and supported in cantilever fashion from the tongs mount 3 in a position between the bifurcations 2 of the crane boom. It is necessary for the motor 24 to be of the reversible type so that it can rotate sprocket 22 positively in each direction by driving chain 23 for turning the nut 18 to raise or to lower the screw 17. Any force exerted on the tongs legs 1a and 1b by a load clamped between them, which tends to spread the tongs legs, will simply tend to pull screw 17 downward with only a negligible component of the force tending to rotate it. Consequently, the screw 17 locks the tongs legs automatically in any selected position.

The axial force exerted on screw 17 by a load clamped between the tongs legs may make it difficult to turn the nut 18 relative to the screw and cause wear of these parts. Consequently, it is desirable to provide a housing 26 carried by the sprocket 22, which completely encloses the portion of the screw projecting upward above the nut 18. Such housing can be filled with lubricant through a self-sealing grease fitting 27.

In operation, the motor 24 can be energized to drive chain 23 for turning the nut 18 to raise or lower the screw 17 relative to the mount 3 so that the tongs legs are fully opened or fully closed. When the screw 17 has reached such a limit position, further rotation of the motor 24 will swivel the turntable 8 and the tongs supported by it relative to the annular tongs mount 3 into any desired swiveled position relative to the crane boom 2. The motor 24 can then be driven in the direction to open the crane tongs legs if they are not open, after which the crane boom 2 is lowered to place the tongs over a load to be lifted.

While the tongs of the present invention will probably find their greatest usefulness when mounted on a crane boom, such power-operated crane tongs could be supported on the end of a hoisting line or on a heel boom crane, if desired. The drive mechanism for opening and closing the legs of the tongs is very compact and exerts minimum stress on the tongs legs compatible with providing an ample clamping force on the load. No effort is required to be exerted by the actuating means for swinging the tongs legs when they have been moved into load-clamping relationship or into an opened relationship. Consequently, the actuating mechanism described is much lighter than conventional power-actuating mechanism for crane tongs.

Instead of using a screw type of jack for moving the spindle 17' lengthwise to open and close the legs 1a and 1b, a hydraulic jack can be used for this purpose. Tongs employing a hydraulic jack in this way are shown in FIGS. 6, 7, and 8. Leg 1a is primarily supported from parallel upright plates 7a by a pivot 10c, and leg 1b is primarily supported by parallel upright plates 7b by pivot 10d. The plates 7a and 7b are rigidly secured to a central tube 15a by welding.

Such tube has a collar 8' screwed onto its upper end and received within the hollow 9' of a non-rotative supporting ring 3a. The tube 15a supports the tongs legs 1a and 1b and is rotatively supported by the non-rotative ring 3a. For this purpose, the collar 8' threadedly connected to tube 15a rests on an internal flange 3b projecting inward from the lower portion of the ring 3a. In order to facilitate rotation of tube 15a relative to ring 3a, a thin, flat bearing ring 3c of antifriction material, such as Teflon or brass, can be interposed between the lower side of the collar 9' and the upper side of the ring flange 3b.

The non-rotative supporting ring 3a is supported from crane boom members 2 by trunnions 4 projecting diametrically from opposite sides of the supporting ring 3a. The crane tongs legs 1a, 1b and their entire mount can swing relative to the crane boom 2 about the axis of the horizontal trunnions 4. The pivots 10c and 10d for the tongs legs are located below the trunnions 4 and upward movement of the tongs and their supporting tube 15a is limited by the collar or flange 15b welded to the tube for disposition immediately below the internal flange 3b of the ring 3a.

As in the type of tongs shown in FIGS. 1 to 4, inclusive, the pivots 10c and 10d carrying the tongs legs 1a and 1b, respectively, are located a short distance below the trunnions 4. The legs of the tongs shown in FIGS. 6 to 8, inclusive, are swung between the closed position of FIG. 7 and the open position of FIG. 6 by a toggle joint including bars or links 12c and 12d having their adjacent ends disposed in overlapping relationship and connected together by a pivot 14'. The opposite ends of links 12c are connected by a pivot rod 13c to the inner end portion of the tongs leg 1a at a location spaced from pivot 10c and the ends of links 12d remote from pivot 14' are connected to the inner end of tongs leg 1b by pivot rod 13d which is spaced from the main pivot 10d.

In order to swing the tongs legs from the closed position of FIG. 7 to the open position of FIG. 6, it is necessary to exert a force on pivot 14' in a direction tending to move it toward a plane including the axis of pivots 13c and 13d. Such force is applied by reciprocating upright spindle 17' lengthwise, the lower end of which is connected to or bears upon pivot 14'. Downward movement of such spindle operates to expand the toggle joint 12c, 12d forcing pivot rods 13c and 13d apart for swinging the tongs legs 1a and 1b relative to the supporting tube 15a and plates 7a and 7b toward open position.

In the apparatus of FIGS. 6, 7 and 8, the mechanism for reciprocating spindle 17' lengthwise is a hydraulic jack connected to the upper portion of the spindle. The lower portion of the spindle is guided for reciprocation relative to the rotative supporting tube 15a by pivotally connecting the lower portion of the spindle to the central portion of the pivot 14', which pivot connects the overlapping adjacent ends of the toggle lengths 12c and 12d and extends through guide slots 15c in opposite sides of the rotative tube 15a. The upper portion of the spindle 17' slides through an aperture in the lower cylinder head 28 of the hydraulic cylinder and carries the piston 18' fitting within a cylindrical tube 29 to form the jack plunger.

The cylindrical tube 29 is clamped between the lower cylinder head 28 and the upper cylinder head 30 of the hydraulic jack cylinder by tie rods 31 having their lower end portions extending through apertures in the margin of the lower cylinder head 28 and their lower ends screwed into the upper side of non-rotative ring 3a. The upper end portions of such tie rods extend through apertures in the marginal portion of the upper cylinder head 30, and such upper end portions are threaded to receive nuts for securing the cylinder head. Consequently, the cylinder 28, 29, 30, being secured to ring 3a, will be held against rotation. The spindle 17' and piston 18', being integrated through pivot 14' with the rotatable tube 15a, will be rotatable with the tongs relative to the cylinder.

While the fluid jack for reciprocating spindle 17' is of the double-acting type, it is not necessary to be able to supply the same fluid pressure above the piston 18' as below the piston. The principal requirement is to be able to exert sufficient fluid pressure in the portion of the cylinder below the piston 18' so as to be able to close the tongs legs 1a and 1b positively on a log or a group of logs and to hold the tongs legs clamped securely around the log load while the crane is handling them. For this purpose it is preferred to supply hydraulic liquid through the connection 32 to the lower end of the cylinder at a pressure within the range of 1500 pounds per square inch to 2250 pounds per square inch. Such pressure will assure that the spindle 17' will be pulled upward to close the tongs legs 1a and 1b forcibly on the log load.

As long as the hydraulic pressure is maintained in the portion of the jack cylinder beneath the piston 18', force will be exerted on the toggle joint 12c, 12d to hold the tongs legs clamped tightly around the load. When it is desired to release the load from the tongs, the supply of hydraulic liquid under pressure to the cylinder connection 32 is discontinued and the weight of the load would probably be sufficient to force the tongs legs open far enough so that the load would drop from the tongs.

It is desirable to spread the legs 1a and 1b open positively when placing the tongs legs in position to grip a load. Such spreading of the tongs legs can be effected by exerting a relatively small force on the toggle joint to expand it. For this purpose a source of air under pressure can be connected to the fluid connection 33 at the upper end of the cylinder. Such opening of the tongs can be accomplished by an air pressure of 100 pounds per square inch, for example.

It is not necessary to provide valve mechanism for supplying and interrupting the supply of air under pressure to the connection 33. Instead a source of air under 100 pounds-per-square-inch pressure can be connected continually to the connection 33 so that there will always be air pressing on the upper side of piston 18' with a force sufficient to swing the tongs legs 1a, 1b to open position when the hydraulic pressure on the lower side of the piston has been substantially completely relieved.

When the tongs are to be closed for gripping a load, it is not necessary to cut off the supply of air under pressure to the upper end of the cylinder because the hydraulic pressure applied through connection 32 to the underside of the piston 18' of the order of 1500 pounds per square inch to 2250 pounds per square inch is so much greater than the pressure of the air on the upper side of the piston that the differential pressure will always effect forcible closing of the tongs legs 1a and 1b to grip a load securely between them. The supply of air under pressure to connection 33, which can be provided by a pressure tank, will not be cut off, and the portion of the cylinder above piston 18' will not be vented during a tongs-closing operation. It is, therefore, only necessary to provide control valve mechanism for supplying hydraulic liquid under pressure to the connection 32 or for connecting the connection 32 to a receiver for draining hydraulic fluid from the portion of the cylinder beneath piston 18' in order to effect opening and closing of the tongs legs.

While it has been proposed above to provide a continual supply of air under a constant pressure to the connection 33 for effecting opening movement of the tongs legs, a compression spring reacting between the upper side of piston 18' and the lower side of the upper cylinder head 30 could be substituted for air under pressure to exert a downward force on spindle 17' to open the tongs legs.

Claims

We claim:

1. In crane tongs including non-rotative supporting means, rotative supporting means rotatable about an upright axis relative to the nonrotative supporting means, crane boom means, means supporting the non-rotative supporting means from the crane boom means, a pair of legs, pivot means carried by the rotative supporting means and supporting the legs for swinging toward and away from each other, and leg-swinging means carried by the rotative supporting means including an upright spindle, a toggle joint having two links connecting the spindle and the legs and drive means connected to the spindle for effecting lengthwise movement of the spindle in opposite directions relative to the rotative supporting means to swing the legs about the pivot means relative to the rotative supporting means for opening and closing the legs, the improvement comprising the drive means including a rotative member rotatable both to effect rotation of the rotative supporting means relative to the non-rotative supporting means and to effect swinging of the legs about their pivot means relative to the rotative supporting means.

2. In crane tongs defined in claim 1, the spindle is a screw, and the drive means includes a nut held against axial movement and rotatable relative to the rotative supporting means to effect lengthwise elevational reciprocation of said screw relative to said nut.

3. In crane tongs defined in claim 2, the nut is rotatable both to effect rotation of the rotative supporting means relative to the non-rotative supporting means and swinging of the legs about their pivot means relative to the rotative supporting means.

4. Crane tongs comprising non-rotative supporting means, rotative supporting means rotatable about an upright axis relative to said non-rotative supporting means, crane boom means, trunnions projecting from opposite sides of said non-rotative supporting means and supporting said non-rotative supporting means from said crane boom means for tilting relative to said crane boom means about a substantially horizontal axis, a pair of legs, pivot means below said trunnions, carried by said rotative supporting means and supporting said legs for swinging toward and away from each other, and leg-swinging means carried by said rotative supporting means and including an upright screw extending a substantial distance above and below said trunnions and having its lower portion connected to said legs below said pivot means and drive means including a nut held against axial movement and rotatable relative to said rotative supporting means to effect lengthwise elevational reciprocation of said screw relative to said nut in opposite directions to swing said legs about said pivot means relative to said rotative supporting means for opening and closing said legs.

5. The crane tongs defined in claim 4, in which the nut is rotatable both to effect rotation of the rotative supporting means relative to the non-rotative supporting means and swinging of the legs about their pivot means relative to the non-rotative supporting means.

6. Crane tongs comprising non-rotative supporting means, rotative supporting means rotatable about an upright axis relative to said non-rotative supporting means, crane boom means, trunnions projecting from opposite sides of said non-rotative supporting means and supporting said nonrotative supporting means from said crane boom means for tilting relative to said crane boom means about a substantially horizontal axis, a pair of legs, pivot means below said trunnions, carried by said rotative supporting means and supporting said legs for swinging toward and away from each other, and leg-swinging means carried by said rotative supporting means and including a rotative member held against axial movement and rotatable relative to said rotative supporting means both to effect rotation of said rotative supporting means relative to said non-rotative supporting means and to effect swinging of said legs about said pivot means relative to said rotative supporting means for opening and closing said legs.

7. In crane tongs including non-rotative supporting means, rotative supporting means rotatable about an upright axis relative to the non-rotative supporting means, crane boom means, means supporting the non-rotative supporting means from the crane boom means, a pair of legs, pivot means carried by the rotative supporting means and supporting the legs for swinging toward and away from each other, and leg-swinging means carried by the rotative supporting means including an upright spindle, a toggle joint having two links connecting the spindle and the legs and drive means connected to the spindle for effecting lengthwise movement of the spindle in opposite directions relative to the rotative supporting means to swing the legs about the pivot means relative to the rotative supporting means for opening and closing the legs, the improvement comprising the drive means including fluid pressure jack means connected to the upper portion of the spindle and variable in effective length to effect lengthwise elevational reciprocation of the spindle relative to the rotative supporting means, continual pressure means acting on said jack means urging said jack means in the direction to spread the legs, and means for supplying fluid under pressure to said jack means to overcome said continual pressure means and swing the legs in the closing direction.

8. In crane tongs defined in claim 7, the jack means including a piston, the continual pressure means being a compressible gas exerting pressure on one side of said piston, and the means for supplying fluid under pressure including liquid under pressure exerting pressure on the opposite side of said piston.