(19)
(11) EP 0 496 170 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
28.10.1992 Bulletin 1992/44

(43) Date of publication A2:
29.07.1992 Bulletin 1992/31

(21) Application number: 91312034.1

(22) Date of filing: 24.12.1991
(51) International Patent Classification (IPC)5: F04C 2/16, F04C 15/00, F04C 15/04, F04C 2/08
(84) Designated Contracting States:
AT BE CH DE DK ES FR GB GR IT LI LU MC NL SE

(30) Priority: 24.12.1990 US 633455

(60) Divisional application:
93201194.3 / 0560462

(71) Applicant: JAMES RIVER CORPORATION OF VIRGINIA
Richmond, VA 23217 (US)

(72) Inventors:
  • Baran, Mark E.
    Neenah Wisconsin 54956 (US)
  • Couch, Vern W.
    Appleton Wisconsin 54911 (US)
  • Phibbs, David P.
    Appleton Wisconsin 54911 (US)
  • Michalec, George W.
    Pleasantville NY 10570 (US)

(74) Representative: Coleman, Stanley et al
Mathys & Squire 100 Grays Inn Road
London WC1X 8AL
London WC1X 8AL (GB)


(56) References cited: : 
   
       


    (54) Positive displacement pumps


    (57) A positive displacement pump having single or twin crews (2) is disclosed in which the screw flights (34,36,38,40) are formed in the outer surfaces thereof with balancing holes (82) which can be filled with material less dense than that of the screw flights which can each be closed by a cap (84) having an outer surface which is flush with the outer surface of the adjoining flight. Also disclosed for the or each screw flight is a wear measuring port (86) in which a measuring device can be inserted to measure relative wear between the corresponding screw flight and the pump casing. Alternatively a proximity sensor (98) can be located in the measuring port so that wear of the corresponding flight can be dynamically sensed during pump operation. Additionally, the provision of wear strips (122) on the outer surface of and of less than half the width of the screw flight are disclosed as is a fluid pressure feedback control system (119) for the or each screw flight which reduces the pressure differential over a part of the discharge end of each flight.






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