Patent ID: 7013887

Claim:
An absorber pipe, especially for a parabolic collector in a solar heat collecting apparatus, said absorber pipe comprising a central metal pipe ( 3 ); a glass sleeve tube ( 2 ) surrounding said central metal pipe ( 3 ) so that an annular space ( 4 ) is formed between the central metal pipe and the glass sleeve tube ( 2 ); a glass-metal transitional element ( 5 ) on a free end of the glass sleeve tube; and an expansion compensating device ( 10 ) connecting the central metal pipe and the glass-metal transitional element ( 5 ) with each other so as to be slidable relative to each other in a longitudinal direction and to guarantee a vacuum-tight seal between the free end of the glass sleeve tube and the central metal pipe; wherein said expansion compensating device ( 10 ) comprises a folding bellows ( 11 ) and a connecting element ( 15 , 15 ′, 15 ″), said folding bellows ( 11 ) is arranged between the glass-metal transitional element ( 5 ) and the central metal pipe ( 3 ), said folding bellows ( 11 ) extends into said annular space ( 4 ), said folding bellows ( 11 ) has an outer end ( 13 ) and an inner end ( 12 ), said inner end ( 12 ) is arranged within the annular space ( 4 ), said outer end ( 13 ) is arranged outside of the annular space, and said inner end ( 12 ) of said folding bellows ( 11 ) is connected to one end of said connecting element ( 15 , 15 ′, 15 ″); wherein another end of said connecting element ( 15 , 15 ′, 15 ″) opposite to the one end connected to the folding bellows ( 11 ) is either connected to the central metal pipe ( 3 ) or to the glass-metal transitional element ( 5 ); and wherein said folding bellows ( 11 ) and said connecting element ( 15 , 15 ′, 15 ″) extend sufficiently into the annular space ( 4 ) and between the grass sleeve tube ( 2 ) and the central metal pipe ( 3 ), so that said glass-metal transitional element ( 5 ) is protected from radiation which would otherwise reach the glass-metal transitional element ( 5 ) after entering the glass sleeve tube ( 2 ); wherein said glass-metal transitional element comprises a metal section glass-sealed directly within said free end of the glass sleeve tube.