The support plate may be provided with a rib frame structure including a plurality of ribs in a horizontal direction corresponding to a direction of the first tilt shaft and {HEAD ~ a plurality} of {TAIL ~ ribs} in a vertical direction corresponding to a direction of the second tilt shaft 
The support plate may be provided with a rib frame structure including a plurality of ribs in a horizontal direction corresponding to a direction of the first tilt shaft and { HEAD ~ a plurality } of { TAIL ~ ribs } in a vertical direction corresponding to a direction of the second tilt shaft
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