Printing – Antismut device – Anti-offset material application
Patent
1982-11-15
1984-09-11
Burr, Edgar S.
Printing
Antismut device
Anti-offset material application
101 1, 101DIG13, 400119, 400191, 427197, 3461531, B41J 318
Patent
active
044703503
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Impact printers are known, including the typewriter and various devices used for the printout of computer output data. Such devices normally involve positioning the back surface of a recording member such as a paper web against a backing member and positioning an ink bearing ribbon or the like against the front surface of such recording member. A movable member is then impacted against the rear surface of the ribbon. This movable member may comprise a relief alpha numeric character or the like, or may be a planar surface, in which instance relief alpha numeric characters are contained on the contacting surface of the backing member. In either instance pressure is applied in a pattern form corresponding to the relief pattern, causing pressure transfer of ink from the ribbon to the recording member surface.
A disadvantage of prior art impact printing processes is the transfer member or ink bearing ribbon, which is commonly used in repetitive manner. This results in a progressive loss of print density and in the production of copy of irregular density when the ribbon is partially and irregularly worn. In the past it has been proposed to wet the type face with a liquid ink prior to printing of each character, but while such procedure may be usable for printing of computer output, such methods are not readily adaptable to typewriting, particularly when the typewriter is in irregular use.
The present invention overcomes the disadvantages of the prior art impact printing processes in that it does not use an ink bearing ribbon, nor does it use a liquid ink.
DESCRIPTION OF THE INVENTION
The present invention relates to impact printers in general, and particularly to the commonly used typewriter. However, although this disclosure relates predominantly to typewriting, it should be understood that the disclosure is equally applicable to many of the presently known impact printers used for computer output. The disclosure should therefore be read as embracing computer output impact printing in addition to typewriting.
In a typewriter the paper sheet is normally positioned against a roller, known as a platen roller. Such platen roller is normally covered with an elastomeric sleeve to allow equalisation of printing pressure to some extent, and to reduce wear on the type face.
In one embodiment of the present invention the platen roller contains a magnetic or magnetisable core. Dry magnetic toner powder of the pressure fixing type, such as that for instance disclosed in U.S. Pat. No. 3,925,219 of STRONG and our U.S. Pat. application Ser. No. 128,906, now U.S. Pat. No. 4,307,169, is contained in a suitable container below the platen roller. Preferably sensors are provided to activate the magnetic field on the platen roller when a sheet of paper is inserted in the typewriter and to switch off said magnetic field when the sheet of paper is removed from the typewriter.
When the magnetic field is applied to the platen roller the dry magnetic toner powder is attracted towards the platen roller to form a loosely held layer of such powder on the paper sheet. When such powder layer is impacted with the type face the loosely held powder on the paper is pressure fixed thereto in imagewise configuration. As the paper sheet moves through the typewriter the unfused powder contained thereon is retained by the magnetic field in the vicinity of the platen roller. Thus the emerging sheet of paper contains a printed image deposit comprising pressure fixed magnetic toner on an otherwise clean and powder free paper sheet.
In other embodiments the relief type face characters on the type ball or roller or hammers or the like comprise magnetisable material, the pressure fixable magnetic dry toner powder being deposited thereon prior to the character to be printed being contacted with the paper.
In those instances in which it is for some reason not desirable to use magnetic dry toner powder, the type face or platen roller surface may comprise electrostatically chargeable material, or at least the outer surface there
REFERENCES:
patent: 2223907 (1940-12-01), Bronfman
patent: 2495389 (1950-01-01), Sammann
patent: 2558900 (1951-07-01), Hooper
patent: 3526708 (1970-09-01), Leatherman
patent: 3682738 (1972-08-01), Smith
patent: 3683406 (1972-08-01), Howell
Burr Edgar S.
Research Laboratories of Australia PTY Limited
Wiecking David A.
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