US3121904A

US3121904A - Doctors for paper making machines

Info

Publication number: US3121904A
Application number: US182338A
Authority: US
Inventors: Scott Harold Eric Baliol
Original assignee: Vickerys Ltd
Current assignee: Vickerys Ltd
Priority date: 1961-04-07
Filing date: 1962-03-26
Publication date: 1964-02-25
Anticipated expiration: 1981-02-25

Description

Feb. 25, 1964 H. E. B. sco'r'r noc'roas FOR PAPER MAKING mcumss 3 Sheets-Sheet 1 Filed March 26, 1962 Feb. 25, 1964 H. E. B. SCOTT DOCTORS FOR PAPER MAKING MACHINES 3 Sheets-Sheet 2 Filed March 26, 1962 Feb. 25, 1964 H. E. B. SCOTT 3,121,904

DOCTORS FOR PAPER MAKING MACHINES Filed March 26, 1962 s Sheets-Sheet :5

14A 5 Q Q J5 &

United States Patent 3,121,904 DQCTGRS FQR PAPER MAIQNG MACHENES Harold Eric Baliol Scott, The Heath, Weyhridge, England, assignor to Vickerys Limited, London, England Filed Mar. 26, 1962, Ser. No. 182,338 (Ilaims priority, application Great Britain Apr. 7, 1961 4 Claims. (Cl. 15--3t)3) With the increasing speed of papermaking machines and the modern practice of coating the paper web with china clay, titanium dioxide and other fillers to increase the opacity while the paper is being made on the machine, fuzz and dust particles removed from the rolls and especially from the drying cylinders by the doctors create a problem.

The present invention provides a doctor which includes a suction chamber extending lengthwise of the doctor, a number of spaced suction nozzles extending from the suction chamber and terminating in suction orifices situated close to the tip of the doctor blade at the side thereof remote from the roll to which the doctor is applied, the suction nozzles providing a substantially uniform distribution of airflow across the width of the doctor, and a deflector plate extending across the suction nozzles and down to the doctor blade for guiding broken paper web away from the doctor blade and preventing it from bunching-up around the suction nozzles, the deflector plate having openings opposite the suction orifices and forming one side of a closed chamber surrounding the suction nozzles.

Two alternative forms of doctor according to the invention are illustrated, by way of example, in the accompanying drawings in which:

FIG. 1 is a cross section through the first form of doctor,

FIG. 2 is a broken away view looking in the direction of the arrow A in FIG. 1,

FIG. 3 is a section on the line IIIIH in FIG. 2,

FIG. 4 is a cross section through the second form of doctor,

FIG. 5 is a view similar to FIG. 4 showing the deflector plate sprung away from the nozzles and FIG. 6 is a section through one of the suction nozzles taken at right angles to the View shown in FIG. 4.

Like reference numerals designate like parts in all the figures.

Referring first to FIGS. 1-3 the doctor includes a blade 10 and a pressure plate 11 which bears on the blade 10 throughout its width. The blade 10 and pressure plate 11 are mounted in a holder 12 attached to a support 13 which is suitably biased to maintain the tip of the blade 10 in contact with the roll to be doctored.

On the support 13 is mounted a pear-shaped member which defines with the support a suction chamber 14, extending for the full length of the doctor and to which suction is applied by any suitable means. A number of suction nozzles 15 extend forwardly from the chamber 14 and terminate in suction orifices 16 near the tip of the blade 10. The nozzles 15 vary in area across the doctor so as to maintain an even distribution of air flow across the doctor. To this end the size of the suction nozzles 15 increases progressively from the end of the chamber 14 to which suction is applied to the other end of said chamber. The nozzles 15 are located in a closed chamber 17, the ends of which are closed by the end walls of the suction chamber 14 and the front wall of which is formed by a deflector plate 18 which bears at its lower end on the pressure plate 11 and normally abuts against the ends of the nozzles 15 to form a seal preventing the entry of atmospheric air into the chamber 17. The rear wall of the chamber 17 is constituted by a plate 30, secured to the suction chamber 14 by screws 31 and having openings 34 registering with the suction nozzles 15. The nozzles 15 have flanges 32 at their rear ends which are formed with holes 33 to accommodate screws (not shown) for fixing the nozzles 15 to the plate 30. The deflector plate 18 which extends above the tubular nozzles 15 from the suction chamber 14 to the pressure plate 11, has openings 19 in register with the orifices 16. The deflector plate 18 has a smooth surface and guides upwardly over the top of the chamber 14 any broken web, so preventing it from launching-up around the nozzles 15 or other parts of the doctor. The openings 19 have inwardly bent lips 21) at their upper edges in order to prevent the leading edge of the broken web from catching in the openings. When pressure is applied to the blade 10, the deflector plate 18 springs slightly away from the nozzles 15, but since the chamber 17 is closed, air continues to be drawn into the nozzles 15 through the openings 19 without substantial diminution of suction to the openings 19 and the pressure in the chamber 17 is reduced to a value slightly below atmospheric pressure.

The doctor shown in FIG. 4 is very similar to that just described, but in this case the suction chamber is constituted by a tube 14A which makes airtight contact with the support 13 to allow sub-atmospheric pressure to be maintained in the chamber 17' or may be attached to the support 13. As will be noted the nozzles 15 and deflector plate 18' of FIG. 4 difler slightly in configuration from the corresponding parts of FIG. 1. The nozzles 15 are shown in FIG. 6 attached by screws 35 to the tube 14A which constitutes the rear wall of the closed chamber 17 As will be apparent from the foregoing description, it is characteristic of the invention that the suction nozzles are located in a closed chamber which is maintained at sub-atmospheric pressure.

What I claim as my invention and desire to secure by Letters Patent is:

l. A doctor for a roll of a paper making machine comprising a support, a doctor blade carried by said support, a pressure plate also carried by the support and bearing on the doctor blade throughout its length, wall means cooperating with the support to form a suction chamber thereon and extending lengthwise of the doctor blade, a number of spaced tubular suction nozzles extending from said suction chamber towards the doctor blade and terminating in suction orifices situated near the tip of the doctor blade, said suction nozzles providing a substantially uniform distribution of airflow across the length of the doctor, and a closed chamber surrounding said nozzles and having two of its walls defined by the support and by a deflector plate which extends over the suction nozzles from the suction chamber to the pressure plate, said deflector plate guiding broken web away from the doctor blade and over the suction chamber and having openings opposite the suction orifices.

2. A doctor as claimed in claim 1, in which the edges of the openings in the deflector plate remote from the doctor blade are bent inwardly.

3. A doctor as claimed in claim 1, in which the suction chamber is defined by the support and by a pear shaped casing attached to the support.

4. A doctor as claimed in claim 1, in which the wall means is a tube mounted on the support of the doctor to make airtight contact therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,890,473 Scott June 16, 1959 FOREIGN PATENTS 821,490 Great Britain Oct. 17, 1959

Claims

1. A DOCTOR FOR A ROLL OF A PAPER MAKING MACHINE COMPRISING A SUPPORT, A DOCTOR BLADE CARRIED BY SAID SUPPORT, A PRESSURE PLATE ALSO CARRIED BY THE SUPPORT AND BEARING ON THE DOCTOR BLADE THROUGHOUT ITS LENGTH, WALL MEANS COOPERATING WITH THE SUPPORT TO FORM A SUCTION CHAMBER THEREON AND EXTENDING LENGTHWISE OF THE DOCTOR BLADE, A NUMBER OF SPACED TUBULAR SUCTION NOZZLES EXTENDING FROM SAID SUCTION CHAMBER TOWARDS THE DOCTOR BLADE AND TERMINATING IN SUCTION ORIFICES SITUATED NEAR THE TIP OF THE DOCTOR BLADE, SAID SUCTION NOZZLES PROVIDING A SUBSTANTIALLY UNIFORM DISTRIBUTION OF AIRFLOW ACROSS THE LENGTH OF THE DOCTOR, AND A CLOSED CHAMBER SURROUNDING SAID NOZZLES AND HAVING TWO OF ITS WALL DEFINED BY THE SUPPORT AND BY A DEFLECTOR PLATE WHICH EXTENDS OVER THE SUCTION NOZZLES FROM THE SUCTION CHAMBER TO THE PRESSURE PLATE, SAID DEFLECTOR PLATE GUIDING BROKEN WEB AWAY FROM THE DOCTOR BLADE AND OVER THE SUCTION CHAMBER AND HAVING OPENINGS OPPOSITE THE SUCTION ORIFICES.