Convertible level luffing crane

Claim 2

A crane comprising in combination: a base structure including a hoist means, an inner boom having a pivotal mounting on the base structure for movement in a vertical plane, an outer boom pivotally mounted on said inner boom for movement in the same vertical plane, and having a tip end, first means including line and sheave means between the inner boom and the hoist means to swing the inner boom about its pivotal mounting on the base structure, second means including line and sheave means connected between the outer boom and the hoist means to independently swing the outer boom about its pivotal connection with the inner boom, a part of said sheave means of said second means being rotatably supported on said pivotal mounting of said inner boom so that the line of action of Said second means passes through said pivotal mounting of said inner boom on the base structure, said hoist means being operable through said first means and said second means to pivot either boom in a first direction and simultaneously pivot the other boom in the opposite direction, the rate of pivotal movements of said booms being such that the tip end of the outer boom describes an essentially horizontal luffing course.

Claim 3

A crane as defined in claim 1, wherein said hoist means includes a pair of drums and releasable means interconnecting the drums for simultaneous operation, and wherein said line and sheave means includes a line and sheave unit for each drum.

Claim 4

A crane as defined in claim 2, wherein said hoist means further includes: a clutch means for disconnecting at least one of said drums from said interconnecting means, and an individual control for each drum operable, when said clutch is disconnected, to rotate either drum independently of the other, one of said controls being operable, when said drums are interconnected, to cause movement of the tip end of said outer boom to describe said luffing course.

Claim 5

A crane as defined in claim 1, wherein said inner boom is demountable from said base structure, a tower boom is adapted to be interposed between said base structure and the inner boom, and three hoist drums and associated line and sheave means are provided, one hoist drum and its line and sheave means being connected to said tower boom.

Claim 6

A crane as defined in claim 1, wherein the hoist means includes at least three hoist units, a first drive means connecting a pair of hoist units for operation in unison, a second drive means connecting a second pair of hoist units for operation in unison, there being one hoist unit common to both pairs, said inner boom being removably mounted on said base structure, a tower boom adapted to be removably and pivotally interposed between said inner boom and said base structure, each hoist unit being connected to operate one of said booms, respectively, a first luffing control for the first drive means, operable when the inner boom is connected to the base structure, to cause the line of either hoist unit joined by the first means to pay out while simultaneously taking in the line of the mated hoist unit, a second luffing control for the second drive means operable when the tower boom is interposed between the inner boom and the base structure, to cause the line of either hoist unit joined by the second drive means to pay out while simultaneously taking in the line of the mated hoist unit.

Claim 7

A crane structure, comprising: a hoist structure, a first boom structure mounted in pivotal relation to said hoist structure, a second boom structure pivotally connected to said first boom structure, said boom structures being relatively proportioned so that, when rotated at opposite directions about their respective pivotal axes at predetermined relative speeds, the extremity of said second boom structure is caused to describe a luffing course, drum means carried by the hoist structure, line and sheave means extending from the drum means to the inner boom, and line and sheave means extending from the drum means to the second boom structure and having a part of said sheave means being rotatably supported on said pivotal mounting of said inner boom so that the line of action passes through the pivotal connection between the first boom structure and the hoist structure, the two line and sheave means being simultaneously operable to move said booms in opposite directions at said predetermined relative speeds to cause luffing travel at the extremity of the second boom.

Claim 8

A crane structure, comprising: a hoist structure, a first boom structure mounted in pivotal relation to said hoist structure, a second boom structure pivotally connected to said first boom structure, said boom structures being relatively proportioned so that, when rotated at opposite directions about their respective pivotal axes at predetermined relative speeds, the extremity of said second boom structure is caused to describe a luffing course, drum means carried by the hoist structure, line and sheave means extending from the drum means to the inner boom, and line and sheave means extending from the drum means to the second boom structure and having a part of said sheave means being rotatably supported on said pivotal mounting of said inner boom so that the line of action passes through the pivotal connection between the first boom structure and the hoist structure, the two line and sheave means being simultaneously operable to move said booms in opposite directions at said predetermined relative speeds to cause luffing travel at the extremity of the second boom.

Claim 9

A claim as defined in claim 6, wherein said drum means includes a pair of drums, a common drive therefor, and a single control means for the drive.

Claim 10

A crane comprising in combination: a base structure including a hoist means, an inner boom having a pivotal mounting on the base structure for movement in a vertical plane, an outer boom pivotally mounted on said inner boom for movement in the same vertical plane, and having a tip end, first means connected between the inner boom and the hoist means to swing the inner boom about its pivotal mounting on the base structure, said first means including a tension link pivotally connected to said inner boom and line and sheave means connecting the tension link to the hoist means, second means connected between the outer boom and the hoist means to independently swing the outer boom about its pivotal connection with the inner boom, said second means including a tension link and line and sheave means having a part of said sheave means rotatably supported on said pivotal mounting of said inner boom so that a line of action passes through said pivotal mounting of said inner boom on the base structure, said hoist means being operable through said first means and said second means to pivot either boom in a first direction and simultaneously pivot the other boom in the opposite direction, the rate of pivotal movements of said booms being such that the tip end of the outer boom describes an essentially horizontal luffing course.

Claim 11

A crane comprising in combination: a base structure including a hoist means, an inner boom having a pivotal mounting on the base structure for movement in a vertical plane, an outer boom pivotally mounted on said inner boom for movement in the same vertical plane, and having a tip end, first means connected between the inner boom and the hoist means to swing the inner boom about its pivotal mounting on the base structure, said first means including a tension link pivotally connected to said inner boom and line and sheave means connecting the tension link to the hoist means, second means connected between the outer boom and the hoist means to independently swing the outer boom about its pivotal connection with the inner boom, said second means including a tension link and line and sheave means having a part of said sheave means rotatably supported on said pivotal mounting of said inner boom so that a line of action passes through said pivotal mounting of said inner boom on the base structure, said hoist means being operable through said first means and said second means to pivot either boom in a first direction and simultaneously pivot the other boom in the opposite direction, the rate of pivotal movements of said booms being such that the tip end of the outer boom describes an essentially horizontal luffing course.

Claim 12

A crane as defined in claim 8, wherein the base structure includes an upright tower boom having the pivotal mounting for the inner boom at its upper end.