CA1149225A - Doctor blades - Google Patents

Doctor blades

Info

Publication number
CA1149225A
CA1149225A CA000352634A CA352634A CA1149225A CA 1149225 A CA1149225 A CA 1149225A CA 000352634 A CA000352634 A CA 000352634A CA 352634 A CA352634 A CA 352634A CA 1149225 A CA1149225 A CA 1149225A
Authority
CA
Canada
Prior art keywords
doctor blade
carrier plate
strip
plate means
intermediate element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000352634A
Other languages
French (fr)
Inventor
Dke A. Boose
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Application granted granted Critical
Publication of CA1149225A publication Critical patent/CA1149225A/en
Expired legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41FPRINTING MACHINES OR PRESSES
    • B41F9/00Rotary intaglio printing presses
    • B41F9/06Details
    • B41F9/08Wiping mechanisms
    • B41F9/10Doctors, scrapers, or like devices
    • B41F9/1036Clamping and adjusting devices

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Rotary Presses (AREA)
  • Inking, Control Or Cleaning Of Printing Machines (AREA)

Abstract

ABSTRACT
DOCTOR BLADES

A composite doctor blade assembly includes a length of steel strip 21, forming the doctor blade, and a similar but narrower back-up blade 22. The strips 21, 22 are clamped between a resiliently flexible carrier strip 23 and an arched resilient strip 24 held together under tension by ties 25 passing through apertures 23a, 24a. To make the blade assembly longitudinally flexible, the apertures are elongated.
The plate 23 is clamped in a holder between an intermediate element 11 and a bottom element 12 with the interposition of an inter-changeable cylindrical packing element 13. The top element 14 is channel shaped to provide extra rigidity.

Description

The present invention relates to doctor blades, more particularly but not exclusively for stripping excess ink from a rotating printing roll in the surface of which there are arranged depressions for filling with printing ink. The doctor blade is attached to a holder carried by an adjustable apparatus which determines the force with which the doctoring edge of the blade lies against the printing roll. Such blades are exposed to wear and must be changed after a period of use.
A conventional doctor blade consists of a strip which is formed along its length with a thinner forward portion and a thicker rear portion. The thinner forward portion is formed by a comparatively expensive grinding operation.
The free edge of the thinner portion is intended for use as a stripping edge, while the thicker portion is intended for clamping in a standard type of blade holder for the printing machinery in question. The advantage of the thin portion of even thickness is that wear on it can take place without the wear causing any unacceptable alteration of the profile of the scraping or doctoring edge engaging the printing roll.
In long printing runs, the blade may have to be removed, either for replacement due to wear or for cleaning. When changing blades, the blade is removed together with a relatively heavy removable portion of the standard holder and is carried to a place for changing the blade or to a hot steam bath in which the blade is to be cleaned. This work is often arduous, since the weight of the removable holder and the blade attached thereto is considerable, and the walking distance in the printing hall to the work bench or to the steam bath is in many cases so long that the holder portion with the blade needs to be transported on a trolley.
British patent specification no. 1507825 discloses the use of a replaceable strip as a doctor blade. The strip is clamped in a doctor blade holder which is, close to the strip itself, relatively stiff lengthwise.

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Such a holder cannot fully support the doctor blades strip in its effort to maintain even pressure between the doctor blade edge and the printing cylinder. As a result the print quality and the doctor blade life will be low.
US patent specification no. 2007418 also discloses a doctor blade holding assembly for a strip, this holding assembly also being relatively stiff lengthwise with disadvantages. The device is designed for negative doctoring, i.e. scraping the roll, consequently without special requirements a doctor blade for a printing roll.
A preferred embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which:
Fig. 1 is a perspective view of a complete doctor blade and holder, Fig. 2 is an exploded view in cross section, through the complete holder shown in Fig. 1, Fig. 3 is an exploded view in cro~;s section, of the flexible doctor blade sub-assembly, Fig. 4 is a view in cross section of the flexible blade sub-assembly when assembled, as ta~en a]ony line IV-IV in Fig 5, Fig. 5 is a fragmentary plan view of one end of the flexible blade sub-assembly, Fig. 6 is a schematic perspective view of the blade sub-assembly showing the lengthwise flexibility of the sub-assembly, Figs. 7, 9 and 11 are plan views of alternative presser plates, and Figs. 8, 10 and 12 are respective cross sections on the lines VIII, X, and Xll of Figs. 7, 9 and 11.
Figures 1 and 2 show a doctor blade assembly consisting of a flexible doctor blade sub-assembly 2 including the doctor knife blade 21 with its back up blade 22 and a light-weight rigid `holder 1.
As shown in Fig. 1 and 2 the light-weight dGctor blade holder 1 consists of three sheet-metal elements of different cross sections, each accurately straight. The bottom element 12 is formed like a Z and has an upstanding rear flange 12a and a .~.-',~

depending front flange 12b. The middle element 11 is formed as an L having a small depending front flange lla. The top element 14 formed like an inverted U having depending front and rear flanges 14a and 14b. The middle element 11 is clamped to the bottom member 12 by a row of bolts 16a having corresponding nuts 16_. Between the middle element 11 and the bottom element 12 is the clamped flexible sub-assembly, normally permanently. To give the middle member 11 an accurate and straight edge to support the springy flexible blade sub-assembly 2 a metal rod or tube 13 is positioned in the corner of the middle element. A range of rods or tubes 13 of different diameters may be made available to enable the pressure of blade application to be adjusted. The top member 14 completes the holder 1 by giving it stiffness, straight-ness and a convenient overall thickness corresponding to the thickness of the conventional, heavy solid metal holder which the holder replaces. The top member 1~ is clamped to the other two members 11, 12 by means of say four or six bolts 17a with corresponding nuts 17b along the length of the holder. The heads of bolts 17a and 17b are counter-sunk into the bottom member 12 so that the bolt heads lie flush with the bottom suface of the bottom member 12. This surface is direct~d towards the doctor blade holder bed in the printing press unit which is a straight plane parallel to the printing cylinder axis demanding an accurate and plane surface of the doctor blade holder.
The holder is preferably provided with two handles 15a fixed to the holder by means of bolts 15B passing through the top member 14.
The doctor blade 21 is a length of thin, steel strip cut from stock of uniform thickness and is supported by a back-up strip 22 which also is a thin steel strip of uniform thickness but narrower than the doctor blade 21. Both blades are resiiiently clamped, as shown in Fig. 4 in the flexible sub-assembly 2. This consists of a wider flexible carrier plate 23, which is clampable or fixable in the holder 1 or ~4~22~i in a conventional solid metal holder, and a narrower flexible presser plate 24, which is disposed with its front edge almost flush with the front edge of the wider plate 23. Both plates 23, 24 are of spring steel 0.3mm thick (or less). As shown in Fig. 3 the arched narrower plate 24 is transversely curved but can also be bent to a corresponding degree, thus comprising two flat portions at an obtuse angle to each other. The plates 24, 23 are held in position by a plurality of ties 25 arranged in a straight row, and each having a flange 25a at one end in the shape of a bolt head and a groove 25b near the other end to receive a circlip 26.
The free length between the two clamping surfaces presented respectively-by the flange 25a and the circlip 26 is substan-tially greater than the combined thickness of the plates 24, 23 and the blades 22, 21.
This free length of the ties and the curvature of the narrower presser plate 24 are so selected relative to each other that the desired clamping pressure is obtained between the front edge portions of the plates 24, 23.
The elongated holes 24a, 23a of the plates 24, 23 through which the ties 25 pass accurately fit the ties 25 transversely and lie with their extended longer dimensions in a straight row parallel to the edges of the plate 23. This permits convenient insertion of the blades 22, 21 to an accurately determined position by first the back-up blade 22 being inserted up to engagement with the ties 25 and then the doctor blade 21 being inserted up to engagement with the ties 25, which thus also serve as stops for the two blades 22, 21.
The doctor blade 21 consists of a thin, steel strip of constant thickness and width, the thickness of the strip being in the range 0.05 - 0.15 mm. The thickness of the doctor blade is thus so small that the blade 21 can be curved in the plane of Fig. 5, the right hand side of the blade being then wrinkled, enabling the blade to be drawn progressively out from or pressed progressively between the plates 24,23 along the length of the blade, from one end to the other with the aid of a rag.
The back-up blade 22 is normally identical to the doctor blade 21 except for the width which is 1 to 2 mm less than the width of the doctor blade.
Since the doctor blade and the back-up blade consist of thin steel strips, the doctor blade supported by the back-up blade can easily adjust itself to unevenesses on the printing cylinder, and this adjusting capacity is further substantially increased by the two blades being resiliently clamped in the flexible sub-assembly. The flexibility of this sub-assembly is shown in Fig. 6, from which it is clear that the front edge of the flexible sub-assembly 2 has a flexing capacity both lengthwise and crosswise relative to a straight reference line R - R when the holder is fixed straight and stiffly along a line F-F and to the left of this line. This flexibility lengthwise directly results from the elongated holes 23a, 24a, these holes being extended at least 30 percent along the hole-row-axis, both in the wider plate 23 and in narrower plate 24. These holes allow the two plates 23, 24 to slide relatively to one and other when the blade flexes lengthwise, as can be seen in Fig. 6.
The flexible sub-assembly and th~s doctor blade 21 have a slightly greater length than the printing cylinder, so that the blade covers the entire length of the printing cylinder. The back-up blade 22 however may be slightly shorter than the doctor blade as shown in Fig. 5, so that the doctor blade 21 itself can be easily and separately gripped at one end when changing blades.
As shown in Figs. 7 and 8 the presser plate means can alternatively consist of a row of separate sections 124, each having one or more elongated aperture 24a, replacing the single presser plate 24. Alternatively, the presser plate 24 can on the other hand be notched or slotted transversely as shown in Figs. 9 and 10 and FigsO 11 and 12 respectively to increase the lengthwise flexibility of the presser plate still more.

Claims (13)

The embodiments of the present invention in which an exclusive property or privilege is claimed are defined as follows:
1. A doctor blade assembly comprising a resliiently flex-ible carrier plate, said carrier plate having a rearward mounting portion by which it is adapted to be clampingly mounted and a free forward portion, arched presser plate means extending along the carrier plate with its concave side directed towards the carrier plate, said pressure plate means overlying only said forward portion of said carrier plate, a resiliently flexible doctor blade strip of constant thickness clamped between the outer edges of the carrier plate and the presser plate means and a row of ties pass-ing through apertures in the carrier plate and the presser plate means to hold the presser plate means in a stressed condition to clamp the doctor blade strip, the apertures in the carrier plate and presser plate means being elongated to permit lengthwise movement of the ties relative to the carrier plate and/or the presser plate means.
2. An assembly according to claim 1, wherein the presser plate means comprises a continuous arched resilient strip.
3. An assembly according to claim 2, wherein the pressure plate strip is transversely slotted or notched.
4. An assembly according to claim 1, wherein, the pressure plate means comprises a plurality of short length of arched resil-ient strip.
5. An assembly according to claims 1, 2 or 3 wherein a resilient flexible backing strip, narrower than the doctor blade strip, is located between the presser plate means and the doctor blade strip.
6. An assembly according to claims 1, 2 or 3 wherein the ties each comprise a separate tie rod having a head at one end and a groove near the other end, the groove receiving a circlip.
7. An assembly according to Claim 4 wherein a resilient flexible backing strip, narrower than the doctor blade strip, is located between the presser plate means and the doctor blade strip.
8. An assembly according to claim 4 wherein the ties each comprise a separate tie rod having a head at one end and a groove near the other end, the groove receiving a circlip.
9. An assembly according to claim 1, including a holder for fixedly supporting the carrier plate, the holder including a platelike intermediate element, a channel-shaped top element having front and rear downwardly projecting flanges bearing on said intermediate element, said intermediate element having a width greater than the top element, a bottom element posi-tioned below and subtantially overlying the intermediate element, the bottom element having an upstanding rear flange which is located behind and overlaps the rear flange of the top element, the bottom element also having a depending front flange which is positioned below a forward portion of the intermediate element, the carrier plate having the rear portion thereof clampingly held between the intermediate and bottom elements so that the carrier portion projects out-wardly beyond the forward edge of the intermediate element, said arched presser plate means being positioned forwardly of said intermediate element, and means for clamping the three elements together so that the carrier plate is clamped between the forward portions of the intermediate and bottom elements.
10. An assembly according to claim 9, wherein the doctor blade strip is held in position solely due to its being resiliently clampingly held between the arched presser plate means and said carrier plate, and a resilient flexible backing strip disposed in overlying relationship to the doctor blade strip and clampingly held between the presser plate means and the doctor blade strip, said flexible backing strip being narrower than the doctor blade strip.
11. An assembly according to claim 9, wherein the front portion of the intermediate element projects forwardly a substantial distance beyond the front flange of the lower element, said intermediate element at its forward edge terminating in a short downwardly directed flange for angularly deflecting the front portion of the carrier plate downwardly relative to that portion of the carrier plate which is clampingly held between the intermediate and bottom elements.
12. A holder and doctor blade assembly, comprising a top channel-like element having front and rear downwardly pro-jecting flanges bearing on an intermediate element in the form of a plate of width greater than the top element, a bottom element having a plate portion which overlies the underside of the intermediate element, the bottom element having an upstanding rear flange which is disposed behind the rear flange of the top element and a depending front flange positioned below a forward region of the intermediate element, a resiliently flexible carrier plate having a rear portion which is clampingly positioned between the inter-mediate member and the plate portion of the lower member, said carrier plate having a front portion which projects outwardly a substantial distance beyond the forward edge of the intermediate element, means for clamping the three elements together with the rear portion of the carrier plate clamped between the forward portions of the intermediate and bottom elements, arched presser plate means extending along the forward edge of the carrier plate with its concave side directed toward the carrier plate, a resiliently flexible doctor blade strip of constant thickness resiliently clamped between the forward portion of the carrier plate and the presser plate means adjacent the outer edges thereof, said doctor blade strip projecting forwardly beyond said latter edges, and a row of ties passing through apertures in the carrier plate and the presser plate means to hold the presser plate means in a stressed condition to resiliently clamp the doctor blade strip therebetween.
13. A holder according to claim 12 wherein the forward portion of the intermediate element has a short depeding flange to form a cover to receive a cylindrical packing element whereby to adjust the positioner of a doctoring edge of the doctor blade.
CA000352634A 1979-05-25 1980-05-23 Doctor blades Expired CA1149225A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7918290 1979-05-25
GB7918290A GB2049555B (en) 1979-05-25 1979-05-25 Doctor blades

Publications (1)

Publication Number Publication Date
CA1149225A true CA1149225A (en) 1983-07-05

Family

ID=10505447

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000352634A Expired CA1149225A (en) 1979-05-25 1980-05-23 Doctor blades

Country Status (4)

Country Link
EP (1) EP0020106B1 (en)
CA (1) CA1149225A (en)
DE (1) DE3070145D1 (en)
GB (1) GB2049555B (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3314356A1 (en) * 1983-04-20 1984-10-25 Paul 8000 München Schiller SPRING Squeegee holder with self-grinding squeegee tape for gravure printing
DE9109787U1 (en) * 1991-08-07 1991-09-26 J.M. Voith Gmbh, 7920 Heidenheim Clamping device for blades, especially in coating machines
SE526497C2 (en) 2003-12-30 2005-09-27 Akeboose Internat Ab Razor blade system, razor blade clamping device, chamber rocker system, printing plant, seduction for clamping a razor blade, and method for connecting a clamping part of a chamber razor

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB287565A (en) * 1927-03-25 1929-05-30 Seming Eriksen Akre Improvements relating to scrapers for cylinders and rollers for paper making machines, calenders and similar machines
DE557556C (en) * 1927-03-25 1932-08-25 Saeming Eriksen Akre Scrapers for drums and rollers on paper machines, calenders, etc. like
US2086075A (en) * 1935-07-11 1937-07-06 Calico Printers Ass Ltd Doctor for use in printing machines

Also Published As

Publication number Publication date
EP0020106B1 (en) 1985-02-13
GB2049555B (en) 1983-04-27
DE3070145D1 (en) 1985-03-28
GB2049555A (en) 1980-12-31
EP0020106A1 (en) 1980-12-10

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