US3559229A

US3559229A - Doctor assembly

Info

Publication number: US3559229A
Application number: US785199A
Authority: US
Inventors: Donald B De Noyer
Original assignee: Allis Chalmers Corp
Current assignee: Allis Chalmers Corp
Priority date: 1968-12-19
Filing date: 1968-12-19
Publication date: 1971-02-02
Anticipated expiration: 1988-02-02

Abstract

A DOCTOR IS DISCLOSED HAVING A PIVOTABLE DOCTOR BACK PARALLEL TO AND SPACED FROM A ROLL OF A PAPER MAKING MACHINE. A BLADE CARRIED BY A BLADE HOLDER IS RESILIENTLY CONNECTED TO THE DOCTOR BACK BY A THIN PLATE OF SUBSTANTIAL WIDTH AND SUFFICIENT LENGTH RELATIVE TO ITS THICKNESS SO AS TO BE RESILIENT AND SUPPLEMENT THE RESILIENCY OF THE BLADE FOR IMPROVED CONTOUR FOLLOWING AND PRESSURIZED SCRAPING OF THE ROLL. THE THIN PLATE, MADE UP OF SEVERAL SEGMENTS ABUTTING EACH OTHER ALONG EDGES NORMAL TO THE ROLL, EXTENDS THE FULL WIDTH OF THE ROLL AND COVERS THE SPACE BETWEEN THE ROLL AND DOCTOR BACK. THE BLADE HOLDER COMPRISES SEGMENTS WHICH OVERLAP THE PLATE SEGMENT, WITH ADJACENT BLADE HOLDER SEGMENTS HELD IN ALIGNMENT FOR BLADE INSERTION AND REMOVAL, BY AN OVERLAPPED PLATE SEGMENT.

Description

D. B. DE NOYER Feb. 2, i 911 DOCTOR ASSEMBLY Filed Dec. 19, 1968 United States Patent Office 3,559,229 Patented Feb. 2., 1971 U.S. Cl. -25651 1 Claim ABSTRACT OF THE DISCLOSURE A doctor is disclosed having a pivotable doctor back parallel to and spaced from a roll of a paper making machine. A blade carried by a blade holder is resiliently connected to the doctor back by a thin plate of substantial width and suflicient length relative to its thickness so as to be resilient and supplement the resiliency of the blade for improved contour following and pressurized scraping of the roll. The thin plate, made up of several segments abutting each other along edges normal to the roll, extends the full width of the roll and covers the space between the roll and doctor back. The blade holder comprises segments which overlap the plate segments, with adjacent blade holder segments held in alignment for blade insertion and removal, by an overlapped plate segment.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS I have copending patent applications related to the type of apparatus disclosed herein and entitled Double Cantilever Supported Doctor Blade Ser. No. 785,200 and Doctor Blade Holding Assembly Ser. No. 785,198 which were both filed concurrently with this application.

BACKGROUND OF THE INVENTION Field of the invention This invention relates generally to apparatus used in paper making machines and in particular to doctors which are used to scrape pulp and water from breast rolls in fourdriniers or forming cylinders in cylinder machines,

. wet broke and water from press rolls, and web crumbs from rolls and drums in web drying assemblies.

Description of the prior art Arrangement for applying doctor blades to the surfaces of rolls in paper making or calendering machinery have been disclosed in many prior art patents beginning perhaps with U.S. Pat. 242,753 of 1881. Although U.S. Pat. 2,191,366 of 1940 disclosed aflexible strip doctor blade yieldably held against a roll surface by a resilient blade holder, it remained for my own U.S. Pat. 3,387,317 of 1968 to disclose a roll and a flexible strip doctor blade held in blade holders for endwise insertion and removal along a path parallel to the roll, with resilient rods of substantial length connecting each blade holder to a doctor back, so that the flexibility of the rods supplemented the flexibility of the blade itself to provide improved contour following and uniform pressure characteristics of the blade on the roll surface. As paper making machines have continued to become larger and wider rolls of 300 to 400 inches wide or more are now needed where rolls of substantially less width were used in the past. Continued innovation in the field of this invention is therefore necessary in order to provide satisfactory doctoring of such large rolls. The objects of the present invention such as are hereinafter set forth are therefore directed to further improvements and advances in the state of the art illustrated by these prior art patents and in particular my own U.S. Pat. 3,387,317.

SUMMARY OF THE INVENTION An object of the present invention is to provide a doctor assembly with improved roll contour following and pressurized scraping characteristics.

Another object of the present invention is to provide a doctor assembly with an improved cantilever support for a blade holder and blade, which will eliminate a need for preloading blade holders in order to insert blades and eliminate a need for protective covering structure such as has been required with certain commercially popular prior art structures including my own U.S. Pat. 3,387,317 in order to prevent water or crumbs traveling over the blade holder and landing back on the roll from which such water or crumbs had been removed.

Another object of the present invention is to provide a new and improved doctor assembly in which the segments of a segmented blade holding means are maintained in alignment for blade insertion and removal.

According to a preferred embodiment of the present invention a doctor blade is carried by a blade holder which is in turn connected to a doctor back by a thin plate spring of substantial width and sufficient length relative to its thickness so as to be resilient and supplement the resiliency of the blade for improved contour following and pressurized scraping of the roll. The thin plate, made up of several segments abutting each other along edges normal to the roll, extends the full width of the roll and covers the space between the roll and doctor back and the plate presents a flat continuous and imperforate surface requiring no protective cover. The blade holder comprises segments which overlap the plate segments, with adjacent blade holder segments held in alignment for blade insertion and removal, by an overlapped plate segment.

Other features and objects of the invention that have been attained will appear from more detailed description of the invention to follow with reference to an embodiment of the present invention shown in the drawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing shows a fragmentary perspective view of a paper making machine roll and doctor assembly according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing a doctor assembly 1 is provided with a doctor back 2 parallel to and spaced from a roll 3 of such as a paper making machine. The back 2 is mounted on means (not shown) to pivot about the axis 4. An actuating means (not shown) is connected to the back 2 to selectively rotate the back clockwise or counterclockwise as indicated by the arrows 5 and 6.

The assembly 1 is provided with a resilient blade 10 extending along the entire width of roll 3 and having a first portion 11 of the blade, i.e., its leading edge, engageable with the surface of roll 3. The blade 10 has a second portion 12, i.e., its trailing edge, with a particular cross sectional configuration, in part thicker than the first portion 11 of blade 10, for a purpose that will appear as this description proceeds.

A blade holder assembly 15 is provided with a width corresponding to the width of blade 10. The blade holder assembly 15 comprises a plurality of segments 16 each having an upper jaw 17 and lower jaw 18. The jaws 17 and 18 define a forward facing slot 20 and a rearward facing slot 21. The lower jaw 18 is provided with an upturned lip 22 for engaging the thicker part of the trailing portion 12 of blade 10. The blade 10 may be inserted into the cavity 20 by sliding the blade in slot 20 along a path of movement parallel to the axis 4. The lip 22 prevents the blade falling out of slot 20 toward roll. 3. The lip 22 also limits movement of the blade 10 relative to the blade holder assembly 15.

Resilient plate means 30 are provided to connect the doctor back 2 to the blade holder assembly and project from the back 2 toward the roll 3 as a flexible cantilever. The plate means 30 is an assembly of segments 31. In order to provide for plate resiliency to supplement blade resiliency in accordance with objects of this invention, the ratio of the plate length X to plate thickness Y is at least :1 and preferably of the order of 50:1 or more and the doctor back is located to accommodate such length. The width Z of the plate segments 31 is substantial, preferably, at least one-half of the plate length X, as the segments are assembled with

adjacent edges

32, 33 abutting each to provide along with the blade 10 and blade holder assembly 15, a cover over the entire space between the doctor back 2 and roll '3.

The plate segments 31 may be attached to the doctor back 2 by any suitable means and as shown in such means include a lower strip 40 and upper strip 41 defining a slot 42 for holding plate segments 31 and screws 43 secure this assembly to the doctor back 2. The opposite end of plate segments 31 is inserted into the rearward facing slot 21 defined in blade holder segments 16 and secured therein by bolts 44. The segments 31 of the plate means 30 and the segments 16 of the blade holder assembly are arranged relative to each other to provide for

adjacent edges

32, 33 of segments 31 being overlapped by a segment 16 of the 'blade holder assembly 15.

In the assembly and operation of the described apparatus, with the plate segments 31 attached to the doctor back 2 and the blade holder segments 16 attached to the segments 31, the doctor back may be rotated about axis 4 in the direction of arrow 5 to raise the blade holder assembly 15 above roll 3 for convenient insertion or removal of blade 10. A blade 10 can be inserted endwise, that is along a path of motion parallel to the axis 4, into the slot 20 without preloading the blade holder segments 16, as the overlapped and overlapping relationship between the plate segments 16 will maintain at all times the slot 20 in each holder segment 16 in alignment for insertion of a blade 10. With a blade 10' inserted in slot 20, doctor back 2 may be rotated about axis 4 in the direction indicated by arrow 6 until blade 10 contacts the surface of roll 3 with a pressure such as may be selected by the machine opera: tor. With blade 10 making pressure contact with roll 3 the plate segments 31, covering the entire space between doctor back 2 and roll 3, is free to flex and this resiliency supplements the resiliency of the blade 10 to provide for improved performance in the blade following the contour of roll 3 and applying pressure uniformly thereto across the entire width of roll 3.

From the foregoing detailed description of the present invention, it has been shown how the objects of the invention have been attained in a preferred manner. However, modifications and equivalents of the disclosed concepts such as readily occur to those skilled in the art are intended to be included within the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A doctor assembly for a roll in a paper making machine, the doctor assembly comprising:

(A) a doctor back adapted for mounting in parallel spaced arrangement to a paper machine roll;

(B) a resilient blade having a first portion along the entire width thereof for engagement with the surface of the roll;

(C) blade holder means engaging and holding a second portion of the blade along the entire width thereof, said second portion being remote from and parallel to the first portion of the blade;

(D) resilient plate means connecting the doctor back to the blade holder means, said plate means providing a continuous imperforate surface between the doctor back and blade holder means and of a width corresponding to the width of the roll;

(E) the doctor back being adapted for mounting at a location spaced from the roll a distance that provides the plate means between the back and the blade holder means with a cantilevered span projecting from the back toward the roll of a dimension having a ratio to the thickness of the plate means of at least 20:1 to provide a resiliency thereto supplementing the resiliency of the blade for contour following engagement of'the blade with the roll; and in which (F) both the blade holder means and the resilient plate means are assemblies of segments each arranged with abutting edges of adjacent segments being transverse to a central axis through the roll, and the segments of the blade holder means are arranged to locate a segment of the blade holder in overlapping relation to each pair of abutting edges of adjacent plate means segments whereby the segments of the plate means maintain the segments of the blade holder means in alignment for insertion and removal of the blade in the blade holder means.

References Cited UNITED STATES PATENTS 1,561,513 11/1925 Frossard 15256.5l

1,696,119 12/1928 Heisel 15-256.51

2,191,366 2/1940 Buccicone et al. 15-256.51

FOREIGN PATENTS 287,565 5/ 1929 Great Britain 34--12O WALTER A. SCHEEL, Primary Examiner L. G. MACHLIN, Assistant Examiner