Electrophotography – Image formation – Fixing
Patent
1998-11-16
2000-05-30
Grimley, Arthur T.
Electrophotography
Image formation
Fixing
118DIG1, G03G 1520
Patent
active
060700440
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a release agent application means. The release agent application means applies parting liquid onto the surface of a fixing drum of an electrographic printer or copier device working according to the transfer printing principle.
In electrographic printer or copier devices, charge images are generated on an intermediate carrier, for example a photoconductor drum, these then being inked with a developer mix of a developer station on the basis of electrostatic or magnetic forces. The inked charge images are transfer-printed onto a recording medium in the form of single sheets or continuous stock in a transfer printing station and are subsequently thermally fixed. For thermal fixing, U.S. Pat. No. 3,324,791 discloses that a fixing station with two drums between which the carrier of the toner image is moved past be employed. The one fixing drum facing toward the toner image is heated, the other presses the carrier with the toner image against the fixing drum. The toner is then melted in by heat and pressure.
In order to prevent toner from remaining adhering to the surface of the fixing drum, the surface thereof is moistened with parting liquid, for example silicone oil. For applying this parting liquid onto the fixing drum, DE-C-39 42 147 discloses a release agent application mans wherein an application element composed of felt is pressed against the fixing drum by a pressing member extending along the fixing drum. A dosing tube that contains discharge openings in its longitudinal extent is provided at that side of the application element facing away from the fixing drum. Release agent pumped into the dosing tube emerges from the openings and thus proceeds onto the application element.
The application element picks up the release agent and transfers it to the surface of the fixing drum. The absorbency is determined by the material, by the thickness of the material and the degree to which the material is contaminated. Thick fleeces are employed as application elements. These can absorb a specific amount of dirt. With increasing contamination, however, the fleece will allow less and less release agent through to the fixing drum, so that it prevents the delivery of release agent to the fixing drum in the extreme case. For this reason, the fleece is renewed continuously or at chronological intervals. To that end, DE 38 42 147 provides a supply roll on which the fleece is wound. A take-up roll in turn winds up dirty fleece.
The transport speed of the fleece is determined by the constant rotational speed of the take-up roll. The transport speed of the fleece therefore rises with increasing diameter of the take-up roll. The cleaning effect of the fleece increases with the transport speed of the fleece. The transport speed of the fleece is therefore designed such that the lower speed at the start of the fleece is just still adequate in order to achieve an adequate cleaning effect. Although the length of the fleece is relatively slight due to its thickness and the spatial limitations connected therewith, a high transport speed of the fleece that is too high for achieving a satisfactory cleaning effect occurs at the end of the fleece supply. This causes a frequent replacement of the fleece and, thus, short maintenance intervals.
The present invention is therefore based on the object of fashioning a release agent application means for applying release agent to the surface of a fixing drum of an electrographic printer or copier device such that a lengthening of the maintenance intervals is achieved given a constant and dependable cleaning effect.
This object is achieved by the features recited in patent claim 1. Improvements and developments of the invention are recited in subclaims.
The application element is wound on a supply roll. A sensor that acquires the rotational speed, for example in the form of pulses, is coupled to the supply roll. It outputs these pulses to a control unit that in turn controls the speed of a motor that drives the take-up roll. The rotational speeds of both rolls are
REFERENCES:
patent: 4569864 (1986-02-01), McIntyre
patent: 5576821 (1996-11-01), Rasch et al.
patent: 5836532 (1998-11-01), Thompson
Hoffmann Joachim
Huntley Stephen Nicholas
Grimley Arthur T.
Ngo Hoang
OcePrinting Systems GmbH
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