US3788219A

US3788219A - Blade for scraping liquids from a relatively moving surface

Info

Publication number: US3788219A
Application number: US00241003A
Authority: US
Inventors: J Gallagher
Original assignee: AB Dick Co
Current assignee: AB Dick Co
Priority date: 1972-04-04
Filing date: 1972-04-04
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: BR7302383D0; JPS4915504A; DE2316608B2; DK135031B; JPS5129042B2; DE2316608C3; GB1399057A; DE2316608A1; FR2179435A5; CA979286A; DK135031C

Abstract

This invention relates to a scraper blade assembly adapted to scrape liquids from a relatively moving surface, the blade having a triangular cross section including respective front and rear legs joined at an apex to form a scraping ledge, and each of the legs having their respective opposite ends anchored in a support bar adapted to move the scraping ledge toward and away from the relatively moving surface.

Description

United States Patent Gallagher Jan. 29, 1974 [54] BLADE FOR SCRAPING LIQUIDS FROM A 2,097,791 1l/1937 Heller 101/157 RELATIVELY MOVING SURFACE 3,585,932 6/1971 Granger 101/169 X 3,108,539 10/1963 Champion et a1... 101/169 X [75] Inventor: John P. Gallagher, Park Ridge, Ill. 2,774,329 12/1956 Smith 118/104 Assigneez A. B. Dick p y Chicago In 3,113,890 12/1963 Johnson et al l5/256.l5 X [22] Filed: AP 4 1972 FOREIGN PATENTS OR APPLICATIONS [21] A l N 241 003 285,140 2/1928 Great Britain 15/256.51

Primary Examiner-Clyde I. Coughenour [52] US. Cl 101/425, l5/256.51, 10l/l69,

118/104, 118/203 57 ABSTRACT [51] Int. Cl B4lf 35/04 58 Field of Search 101/423-425, 157, T1118 "lvemlon relates to Scraper blade assembly 101,169 156 162 164 165 168 adapted to scrape liquids from a relatively moving sur- 8/164 6 6 7 3 25651 face, the blade having a triangular cross section in- 252553 4 10493 eluding respective front and rear legs joined at an apex to form a scraping ledge, and each of the legs [56] References Cited having their respective opposite ends anchored in a UNITED STATES PATENTS support bar adapted to move the scraping ledge 2 582 359 H1952 Sh 15/256 51 toward and away from the relatively moving surface.

aw 1,269,767 6/1918 White 101/425 5 Claims, 3 Drawing Figures BLADE FOR SCRAPING LIQUIDS FROM A RELATIVELY MOVING SURFACE BACKGROUND OF THE INVENTION Scraper blades for cleaning surfaces of rollers, such as the inking rollers in an offset duplicating machine, are well known in the art. Examples of such prior art blades are shown in Gegenheimer U.S. Pat. No. 2,970,541; Cope et al. U.S. Pat. No. 2,969,735; and Curtis U.S. Pat. No. 2,341,020. The problem with these prior art blades is that any one of them does not solve all of the problems in quickly scraping a liquid such as solvent diluted lithographic ink from a surface such as a roller in the inking system. For example, Gegenheimer U.S. Pat. No. 2,970,541 shows a blade that does not follow an uneven surface as intimately as is desirable for thorough cleaning, and furthermore the blade will apply a braking force to the relatively moving surface increasing the drag on the roller as well as causing excessive wear to the blade. The blade shown in Curtis U.S. Pat. No. 2,341,020 permits a wedge of liquid to build up under the blade so that when the blade is disengaged, the wedge of liquid remains on the roller surface and prevents achieving complete clean up of the surface. The blade shown in Cope et al. U.S. Pat. No. 2,969,735 has similar problems.

OBJECTS AND SUMMARY OF THE INVENTION It is an overall object of the present invention in accordance with the above to provide an economically manufacturable and easily operable blade for removing liquids from a relatively movable surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a scraper assembly embodying the present invention adapted to clean the surface of a roller;

FIG. 2 is an enlarged section of a surface engaging portion of the scraper assembly of FIG. 1; and

FIG. 3 is an elevation, partially in section, of the scraper assembly and roller shown in FIG. 1.

Turning to the drawings and FIG. 1 thereshown is a scraper assembly selectively operable to bring a surface engaging portion, generally referred to as a blade 11, into engagement with a surface to be cleaned, in the present instance a roller 12. For a more detailed description of one application of the scraper assembly, reference is made to a co-pending U.S. Pat. application Ser. No. 241,024, filed Apr. 4, 1972 titled: Improved System for Cleaning Rollers ofA Duplicating Machine, Such As The Inking Rollers, assigned to A. B. Dick Company, assignee of the present invention.

In accordance with the present invention the blade 11 is constructed so that engagement of the latter with a relatively movable surface 14, such as that of roller 11 covered with a liquid 15, effects substantially complete removal of the liquid from the surface, while minimizing the braking effect applied to the relatively moving members. To that end, the blade 11 preferably has a generally triangular cross section (see FIGS. 1 and 2) with a front leg 16 and a rear leg 18, the common ends of the latter being joined at an apex 19 and having individual integral bases or

feet

20 and 21 at their respective opposite ends suitably anchored. The legs are preferably shaped to have a generally curved configuration. Accordingly, the exemplary blade is formed with the legs, apex and feet as one integral item. One exemplary curved or convex shape is represented by the

outer surfaces

22, 24 respectively of the

legs

16 and 18.

To form a scraping ledge 25, the outer surface 22 of leg 16 intersects the apex 19 below the point at which the outer surface 24 of leg 18 intersects the apex. Accordingly, a scraping edge 26 and a scrapings diverting face 28 are provided at the apex for engaging the surface to be cleaned and to penetrate the liquid layer or coating 15 so as to remove the liquid from the surface and direct the scrapings away. Assuming that the viscosity of the liquid is in a range so that it readily flows, the scraping edge is self cleaning, and thus all the scrapings are directed away from the scraping edge. It is a feature of the present invention as explained subsequently that the blade is capable of operating so that the edge 26 will not penetrate a liquid having a viscosity greater than that which will flow when scraped.

The exemplary embodiment shows a support bar 29 for the blade 11, having a pair of

grooves

30, 31, the groove 30 being shaped to captively receive foot 20 and groove 31 being shaped to captively receive the other foot 21. The blade 11 is preferably formed of resilient material such as rubber so that with the bases of the respective legs held captive, a predetermined balance of forces is maintained at the apex 19'.

For moving the blade assembly 11 toward the roller surface 14, the bar 29 of the blade assembly 11 is carried for pivotable movement (counterclockwise as viewed in FIG. 1) by a set of pivot pins 36, 37. The diverting face 28 must confront the surface to be cleaned against the direction of relative movement. That is, with the blade stationary and the roller rotating, the face 28 confronts the roller against the direction of rotation. Initially the stiffness of both

legs

16 and 18 provides the columnar support for the blade ledge 25 to cause the blade edge 26 to penetrate the liquid layer 15 and engage the roller surface. As herein contemplated, the form and the material selected for the legs is such as to penetrate a liquid layer of predetermined viscosity. As those skilled in the art will appreciate from the teachings of the present invention a blade providing greater stiffness or resistance at the scraping ledge 25 will penetrate liquids of greater viscosity.

In one practical instance the blade was brought into engagement with the surface so that the diverting face 28 was inclined at an angle of approximately 15 off perpendicular at the point of scraping. However, it is within the knowledge of one skilled in the art using the teachings of the present invention to select different angles from the latter. As those skilled in the art will appreciate the orientation of the diverting face to the roller surface must be so selected that the blade edge 26 intimately engages the surface to be cleaned and the scraped contaminants are not transferred back to the roller surface as a wedge when the blade is retracted.

Continuing the description of the force balance in the blade, when the blade is first pressed against the surface and the liquid layer is encountered, the front and rear legs l6, 18 respectively are subjected to compression. While there is a hydrodynamic surface present on the roller as provided by a liquid film, or layer, the coefficient of friction between the blade and roller is relatively low. If the liquid layer has a predetermined viscosity the compression forces and bending forces in the legs will cause the blade edge to penetrate the liquid and start scraping. By selecting the physical properties for the blade as exemplified herein, it is possible to effect scraping only of liquids below a predetermined viscosity. In one practical instance where it was undesirable to scrape offset ink but it was desirable to scrape solvent-cut offset ink it was found that the scraping ledge 25 would penetrate only the solvent-cut ink if the rear leg 18 was of greater cross sectional area than the front leg 16. The movement of the blade assembly 35 can be limited, as can be understood by reference to the aforementioned co-pending application, so that when the controls are operated to effect scraping engagement the blade edge 26 is just pressing the roller surface 14. Thus, a layer of high viscosity ink would not be penetrated but solvent-cut ink could be penetrated.

Once scraping is initiated the rear leg is under compression and thereby maintains the blade edge 26 pressed against the surface, while the front leg 16 is under bending forces to assure that the diverting face 28 does not pull away or flex excessively thereby eliminating the scraping effectiveness of the edge 26. The latter is also important to maintain the scraping ledge 25 in uniform contact with the surface to be scraped so that chatter and vibration of the blade is prevented. Accordingly, the blade is protected from being torn-up or disintegrated in high speed operation.

The construction of the rear leg 18 including having the front leg surface 22 intersecting the apex 19 below the point at which the rear leg surface 24 intersects the apex provides a support for the edge 26 and diverting face 28 so that the scraping ledge is maintained in predetermined alignment ancl is not allowed to bend or flex back upon itself, which would be completely unsatisfactory.

The present invention has another feature in that it is fool proof should the blade be pressed against a relatively moving dry surface. To that end, the resistance force under tension provided by the front leg 16 is such as to release the scraping ledge 25 if the friction is too great in the scraping area. Contrariwisc to when a hydro-dynamic surface is present, the lack of a liquid on the surface provides a relatively high coefficient of friction. Accordingly, in the instance of scraping rollers in an offset duplicator, there would not be applied a braking force that would damage the blade or the drive of the rollers.

By having the base of front leg 16 held captive in groove 30 that leg can withstand the tension applied to the leg by the ledge as it scrapes a surface. Also, the groove 31 by holding foot 21 captive assures that the desired lateral spacing between the

legs

16, 18 is maintained to assure the advantageous triangular shape for the blade assembly 11. In the one practical instance described previously the advantageous spacing between

bases

20 and 21 is in the neighborhood of one-fourth of an inch and the leg surface 22 has a contour generated by a radius of one-half of an inch while the leg sur face 24 has a contour generated by a radius of elevensixteenths of an inch.

In the same practical example, the front leg has a thickness of three sixty-fourths of an inch at a point represented by reference character 38, while the rear leg has a thickness of five sixty-fourths of an inch at a point represented by reference character 39 and the diverting face has a dimension of one thirty-second of an inch. It is clear from the foregoing that the inventive blade herein described solves the problems encountered in cleaning duplicating or printing machine surfaces, for example roller surfaces. The thorough cleaning and low application of retarding force is very desirable. Also, the self-cleaning feature of the blade to direct away scrapings is particularly desirable. It is further advantageous that in cleaning surfaces such as those encountered in a system of inking rollers for an offset duplicating machine, the viscosity of the liquid to be scraped is not critical once it is below a predetermined value. Accordingly, the blade can be operated so that ink is not scraped, while ink cut with solvent is scraped.

Though an exemplary embodiment of the present invention describes scraping rollers, it is understood that this is by way of illustration and the scope of my invention includes scraping other relatively movable surfaces, for example belts. In that regard it is also to be understood that the present invention can be used to scrape liquids other than the exemplary solvent-cut lithographic ink as long as the construction and operation of the blade is such as to penetrate the liquid.

I claim as my invention the following:

1. In an apparatus having a surface carrying a liquid to be removed and a scraper assembly including a surface engaging portion of generally triangular cross section made of flexible material and mounted for relative movement with respect to the surface so as to have an apex of the triangular cross section engageable with the surface to remove the liquid, comprising in combination a scraper ledge at the triangle apex having a scraping edge and a scrapings diverting face; spaced apart front and rear legs joined together at, and sloping back and away from said apex; said diverting face being defined by an outer surface of said front leg intersecting the apex at a point below where an outer surface of said rear leg intersects the same apex; and a base remote from said ledge for supporting said front and rear legs in spaced apart relationship.

2. The combination of claim 1 wherein said legs have an arcuate shape and including means supporting said base operative to bring said scraping edge and the surface to be cleaned into scraping engagement.

3. The combination of claim 2 wherein said rear leg has a greater cross sectional area than said front leg to support said ledge as said scraping edge is engaged with the surface to be cleaned and is pressed against that surface.

4. The combination of claim 3 wherein means sup port and retain said base against lateral movement to prevent collapse of said ledge when the surface to be cleaned and the scraping edge are pressed together.

5. The combination of claim 4 wherein said front and rear legs have a generally convex configuration.

Claims

4. The combination of claim 3 wherein means support and retain said base against lateral movement to prevent collapse of said ledge when the surface to be cleaned and the scraping edge are pressed together.