Tower crane with rockable top sector

Claim 2

In a tower crane the combination of a vertically positioned tower boom, a unitary jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position alongside said tower boom and for upward movement into a raised limit position beyond horizontal; and freely articulated link means operatively interposed between said tower and jib booms so as to permit said downward movement of said jib boom into said depending position and prevent said upward movement thereof beyond said limit position, said link means comprising a pair of links hingedly interconnected at relatively adjacent ends thereof; link pivot means at the top of said tower boom and link pivot means on said jib boom spaced predetermined distances, respectively, from said forward pivot means and operatively connected, respectively, with one and the other of said links; the distances of said first and second mentioned link pivot means from said forward pivot means, and the effective lengths of said links being relatively proportioned so that when said jib boom is in said depending position said forward pivot means are straddled by said hingedly interconnected links, and when said jib boom is in said raised limit position one said hingedly interconnected link ends bears against said jib boom above said forward pivot means.

Claim 3

The combination set forth in claim 1 and further comprising means for varying the effective length of said one of said hingedly interconnected links and thereby varying said raised limit position of said jib boom.

Claim 4

The combination set forth in claim 1, wherein said one of said hingedly interconnected links comprises an assembly of telescopically extensible and contractable thrust transmitting elements, and resilient means operatively interposed between said thrust transmitting elements so as to yieldingly resist relative contraction of the latter.

Claim 5

The combination set forth in claim 3, and further comprising an auxiliary thrust transmitting element adapted for selective insertion into and removal from said assembly so as to increase and decrease the effective length of said one of said hingedly interconnected links.

Claim 6

In a tower crane the combination of a vertically positioned tower boom, a unitary jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position alongside said tower boom and for upward movement into a raised limit position beyond horizontal; and freely articulated link meaNs operatively interposed between said tower and jib booms so as to permit said downward movement of said jib boom into said depending position and prevent said upward movement thereof beyond said limit position, said link means comprising a tubular first link member and second link member hingedly interconnected at relatively adjacent ends thereof; a bracket structure secured to said tubular link member and extending lengthwise beyond the free end of the latter, a collar selectively connectable to said bracket structure at different axial spacings from said free end of said tubular link member; an extension element having a rod portion extending telescopically through said collar and into said tubular link member; a coil spring surrounding said rod portion and bearing at its opposite ends against said collar and a shoulder of said extension element; a lost motion connection between said bracket structure and said extension element; link pivot means at the top of said tower boom and link pivot means on said jib boom spaced predetermined distances, respectively, from said forward pivot means and operatively connected, respectively, with said extension element and with the free end of said second link member; the distances of said first and second mentioned link pivot means from said forward pivot means, and said link members and extension element being relatively proportioned so that when jib boom is in said depending position said first pivot means are straddled by said hingedly interconnected link members and when said jib boom is in said raised limit position one of said hingedly interconnected link ends bears against said jib boom above said forward pivot means.

Claim 7

In a tower crane the combination of a vertically positioned tower boom, a unitary jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position alongside said tower boom and for upward movement into a raised limit position beyond horizontal; and freely articulated link meaNs operatively interposed between said tower and jib booms so as to permit said downward movement of said jib boom into said depending position and prevent said upward movement thereof beyond said limit position, said link means comprising a tubular first link member and second link member hingedly interconnected at relatively adjacent ends thereof; a bracket structure secured to said tubular link member and extending lengthwise beyond the free end of the latter, a collar selectively connectable to said bracket structure at different axial spacings from said free end of said tubular link member; an extension element having a rod portion extending telescopically through said collar and into said tubular link member; a coil spring surrounding said rod portion and bearing at its opposite ends against said collar and a shoulder of said extension element; a lost motion connection between said bracket structure and said extension element; link pivot means at the top of said tower boom and link pivot means on said jib boom spaced predetermined distances, respectively, from said forward pivot means and operatively connected, respectively, with said extension element and with the free end of said second link member; the distances of said first and second mentioned link pivot means from said forward pivot means, and said link members and extension element being relatively proportioned so that when jib boom is in said depending position said first pivot means are straddled by said hingedly interconnected link members and when said jib boom is in said raised limit position one of said hingedly interconnected link ends bears against said jib boom above said forward pivot means.

Claim 8

In a tower crane the combination of a vertically positioned tower boom, a unitary jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position alongside said tower boom and for upward movement into a raised limit position beyond horizontal, and freely articulated link means operatively interposed between said tower and jib booms so as to permit said downward movement of said jib boom into said depending position and prevent said upward movement thereof beyond said limit position, said link means comprising a tubular first link member and a second link member hingedly interconnected at relatively adjacent ends thereof; a tubular spacing element having one end in axial abutting engagement with the free end of said tubular link member, a collar in axial abutting engagement with the other end of said spacing element; an extension element having a rod portion extending telescopically through said collar and spacing element into said tubular link member, a coil spring surrounding said rod portion and bearing at its opposite ends against said collar and a shoulder on said extension element; separable lost motion connecting means between said tubular link member and said extension element; link pivot means at the top of said tower boom and link pivot means on said jib boom spaced predetermined distances, respectively, from said forward pivot means and operatively connected, respectively, with said extension element and with the free end of said second link member; the distances of said first and second mentioned link pivot means from said forward pivot means, and said link members and extension element being relatively proportioned so that when said jib boom is in said depending position said forward pivot means are straddled by said hingedly interconnected members, and when said jib boom is in said raised limit position one of said hingedly interconnected link ends bears against said jib boom above said first pivot means.

Claim 9

In a tower crane the combination of a vertically positioned tower boom, a unitary jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position alongside said tower boom and for upward movement into a raised limit position beyond horizontal, and freely articulated link means operatively interposed between said tower and jib booms so as to permit said downward movement of said jib boom into said depending position and prevent said upward movement thereof beyond said limit position, said link means comprising a tubular first link member and a second link member hingedly interconnected at relatively adjacent ends thereof; a tubular spacing element having one end in axial abutting engagement with the free end of said tubular link member, a collar in axial abutting engagement with the other end of said spacing element; an extension element having a rod portion extending telescopically through said collar and spacing element into said tubular link member, a coil spring surrounding said rod portion and bearing at its opposite ends against said collar and a shoulder on said extension element; separable lost motion connecting means between said tubular link member and said extension element; link pivot means at the top of said tower boom and link pivot means on said jib boom spaced predetermined distances, respectively, from said forward pivot means and operatively connected, respectively, with said extension element and with the free end of said second link member; the distances of said first and second mentioned link pivot means from said forward pivot means, and said link members and extension element being relatively proportioned so that when said jib boom is in said depending position said forward pivot means are straddled by said hingedly interconnected members, and when said jib boom is in said raised limit position one of said hingedly interconnected link ends bears against said jib boom above said first pivot means.

Claim 10

In a tower crane, the combination of a vertically positioned tower boom; a jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position along the forward side of said tower boom and for upward movement into a raised position beyond horizontal; a sector sHaped rocker structure having a hub portion and an arcuate peripheral portion presenting first and second corners at its opposite ends; rearward pivot means at the top of said tower boom mounting said rocker structure at said hub portion thereof for forward swinging movement into a raised position in which said first corner thereof overhangs said tower boom at its forward side and said second corner is positioned above said rearward pivot means, and for rearward swinging movement into a lowered position in which said first corner of said rocker structure overhangs said tower boom at its rearward side and said second corner is positioned in proximity to the latter; a pendant connected at its opposite ends to said first corner of said rocker structure and to the peak of said jib boom; a control cable anchored at one end thereof to said first corner of said rocker structure and movable upon and from said arcuate peripheral portion of said rocker structure; a link member pivotally connected with the other end of said control cable and adapted to bear upon said second corner of said rocker structure while the latter is in said raised position; a hoist cable pivotally connected with said link member; and roller means on said link member and track means connected with said rocker structure at said second corner thereof for cooperative engagement with said roller means during swinging movement of said rocker structure into said raised position, and for separation of said track means from said roller means during swinging movement of said rocker structure into said lowered position.

Claim 11

In a tower crane, the combination of a vertically positioned tower boom; a jib boom, forward pivot means at the top of said tower boom mounting said jib boom for downward movement into a depending position along the forward side of said tower boom and for upward movement into a raised position beyond horizontal; a sector sHaped rocker structure having a hub portion and an arcuate peripheral portion presenting first and second corners at its opposite ends; rearward pivot means at the top of said tower boom mounting said rocker structure at said hub portion thereof for forward swinging movement into a raised position in which said first corner thereof overhangs said tower boom at its forward side and said second corner is positioned above said rearward pivot means, and for rearward swinging movement into a lowered position in which said first corner of said rocker structure overhangs said tower boom at its rearward side and said second corner is positioned in proximity to the latter; a pendant connected at its opposite ends to said first corner of said rocker structure and to the peak of said jib boom; a control cable anchored at one end thereof to said first corner of said rocker structure and movable upon and from said arcuate peripheral portion of said rocker structure; a link member pivotally connected with the other end of said control cable and adapted to bear upon said second corner of said rocker structure while the latter is in said raised position; a hoist cable pivotally connected with said link member; and roller means on said link member and track means connected with said rocker structure at said second corner thereof for cooperative engagement with said roller means during swinging movement of said rocker structure into said raised position, and for separation of said track means from said roller means during swinging movement of said rocker structure into said lowered position.