Auxiliary boom, crane, method for unfolding auxiliary boom and method for retracting auxiliary boom

An auxiliary boom, comprising:

• an auxiliary boom body comprising a connecting frame;
• the connecting frame comprises a first connecting hole and a second connecting hole which are coaxially arranged;
• and
• a jackscrew mechanism comprising a first shaft, a second shaft and a driving mechanism;
• the first shaft and the second shaft are both arranged between the first connecting hole and the second connecting hole and coaxial with the first connecting hole;
• the driving mechanism is in driving connection with both the first shaft and the second shaft to drive the first shaft and the second shaft to protrude simultaneously and retract simultaneously;
• wherein when the first shaft is in a protruded state, the first shaft is inserted into the first connecting hole;
• when the first shaft is in a retracted state, the first shaft leaves the first connecting hole;
• when the second shaft is in the protruded state, the second shaft is inserted into the second connecting hole;
• and when the second shaft is in the retracted state, the second shaft leaves the second connecting hole,
• wherein the driving mechanism comprises:
• a first connecting seat fixedly connected to the connecting frame and provided with a first through hole allowing the first shaft to pass through;
• a second connecting seat fixedly connected to the connecting frame and provided with a second through hole allowing the second shaft to pass through;
• and
• a drum arranged between the first connecting seat and the second connecting seat and rotatably connected to at least one thereof;
• wherein an end of the first shaft facing the drum is provided with a first thread, a first end of the drum is correspondingly provided with a first thread segment in a thread fit with the first thread, and the first shaft is located in the first through hole;
• an end of the second shaft facing the drum is provided with a second thread, and a second end of the drum is correspondingly provided with a second thread segment in a thread fit with the second thread, and the second shaft is located in the second through hole;
• a screwing direction of the first thread is opposite to that of the second thread;
• wherein the driving mechanism further comprises:
• a first bearing, an inner ring of which is arranged to sleeve the drum;
• a first end cover with a first concave portion, and the first end cover is fixedly connected to an outer ring of the first bearing and the second connecting seat;
• and
• a second end cover with a second concave portion, and the second end cover is fixedly connected to the outer ring of the first bearing and the second connecting seat;
• wherein the first concave portion and the second concave portion are spliced together to form a mounting cavity for accommodating the first bearing.