(19)
(11) EP 0 830 934 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
05.08.1998 Bulletin 1998/32

(43) Date of publication A2:
25.03.1998 Bulletin 1998/13

(21) Application number: 97202514.2

(22) Date of filing: 24.12.1991
(51) International Patent Classification (IPC)6: B29D 30/00
(84) Designated Contracting States:
DE ES FR GB IT

(30) Priority: 24.12.1990 US 633455

(62) Application number of the earlier application in accordance with Art. 76 EPC:
93201194.3 / 0560462
91312034.1 / 0496170

(71) Applicant: FORT JAMES CORPORATION
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: Cozens, Paul Dennis et al
Mathys & Squire 100 Grays Inn Road
London WC1X 8AL
London WC1X 8AL (GB)

 
Remarks:
This application was filed on 14.08.1997 as a divisional application to the application mentioned under INID code 62.
 


(54) Positive displacement pumps


(57) A positive displacement pump having single or twin screws (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.






Search report