Patent ID: 7374139

Claim:
A retractable support tube structure ( 1 ) positioned between a base and a steering mechanism, comprising: an upright tube ( 10 ), having a rectangular cross section with a longitudinal receiving space ( 11 ) formed centrally, a bottom end ( 10 a ) fixedly fastened to said base, a top end ( 10 b ) extending along a vertical direction; a first friction member ( 20 ) having an outer race ( 20 a ), an inner race ( 20 b ), and a coupling groove ( 21 ) defined between the outer race ( 20 a ) and inner race ( 20 b ) of said first friction member ( 20 ) and coupled to the top end ( 10 b ) of said upright tube ( 10 ); an telescopic arm ( 30 ), having a square cross section with a hollow portion ( 31 ) formed centrally, a bottom end ( 30 a ) inserted in said longitudinal receiving space ( 11 ) of said upright tube ( 10 ) and an outer periphery urged against said inner race ( 20 b ) of said first friction member; a second friction member ( 40 ) having an outer race ( 40 a ) urged against an inner periphery of said longitudinal receiving space ( 11 ) of said upright tube ( 10 ), an inner race ( 40 b ), a coupling groove ( 41 ) defined between said outer race ( 40 a ) and inner race ( 40 b ) of said second friction member ( 40 ) and coupled to said bottom end ( 30 a ) of said telescopic arm ( 30 ); and a spring member ( 50 ) mounted inside said longitudinal receiving space ( 11 ) of said upright tube ( 10 ), having a first end fastened to said inner periphery inside said longitudinal receiving space ( 11 ) and a second end coiled up to form a helical spring portion ( 51 ) and stopped against the bottom side of said second friction member ( 40 ).