The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 03, 2001
Filed:
Apr. 12, 1999
Friedrich Wilhelm Dannehl, Hagen, DE;
Werner Reinelt, Bochum, DE;
DBT Deutsche-Bergbau Technik GmbH, Lunen, DE;
Abstract
The double telescopic prop comprises an outer cylindrical casing tube,, an inner tube,which is displaceable therein and a piston rod,which can be extended therefrom. The hydraulic fluid for extending the two prop stages is conveyed through a connection,to the piston,of the inner tube,and is conveyed via a bottom valve to the piston,of the piston rod,. The prop is retracted if hydraulic fluid flows via the connection,into the outer annulus,between the cylindrical casing tube,and the inner tube,. A size ratio of 8.8:1 at most, which is favourable for the retraction of the prop, exists between the area of the inner tube,and the ring area of the annulus