Electrophotography – Document handling – Copy
Patent
1996-10-22
1998-05-12
Grimley, Arthur T.
Electrophotography
Document handling
Copy
226 24, 399322, G03G 1500
Patent
active
057521530
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a system and a process for avoiding slip during transport of a recording substrate in an electrographic printer or copier. In electrographic printers or copiers, recording substrates in continuous form are conveyed to various units which are arranged along a recording substrate transport path. In order to ensure secure transport of the recording substrate, recording substrates are often used which have an edge perforation. Tractor drives, with the aid of which the recording substrate is able to be transported without slip within specific tolerance levels, engage in the edge perforation.
In the region of the fixing device, particular requirement are placed in relation to slip-free recording substrate transport. In a fixing device, such as is known, for example, from U.S. Pat. No. 4 147 922, the recording substrate is therefore transported by friction between a nip roller and a fixing roller. At least one of the two rollers, which are pressed against each other, is driven by a motor for this purpose. During the passage between the two rollers, of which at least one is heated, a toner image loosely applied on the recording substrate is fused into the recording substrate.
In the case of simple transport of the recording substrate through between the fixing roller and the nip roller, the formation of folds in the recording substrate may occur because of the influence of heat and the high pressure. Therefore, the recording substrate is tautened before passage between the fixing roller and the nip roller. For this purpose, in the recording substrate transport direction, a sliding saddle and a paper brake are provided upstream of the two rollers. The sliding saddle is located between the rollers and the paper brake. The paper brake, which is operated under vacuum, sucks the recording substrate on and brakes the latter more or less severely according to the available vacuum. The force in the recording substrate transport direction which is brought about by the friction between the fixing roller and nip roller counteracts the force which is brought about by the paper brake. The recording substrate is tensioned over the saddle.
The recording substrate is led to the paper brake at constant speed over the recording substrate transport path. In order to equalize temporary differences in the recording substrate transport speed, a loop tensioner is arranged upstream of the paper brake.
Such a loop tensioner is known from WO reference 91/09352. The position of the loop tensioner is scanned by two sensors which are arranged in the region of the maximum and minimum deflection of the loop tensioner. The rotational speed of the rollers which are transporting the recording substrate and are arranged upstream and downstream of the loop tensioner is controlled as a function of the respective position.
It has now been shown that, in the case of the known devices, slip can occur between at least one of the fixing roller and the nip roller and the recording substrate. This slip occurs when the friction between the recording substrate and the saddle and paper brake is greater than the friction between the recording substrate and the rollers. This unfavorable friction behavior has its causes in thermal expansion of the fixing and nip rollers, the oiling up of the fixing roller, uneven nip forces along the fixing and nip rollers and/or in the properties of the recording substrate being processed. Smudging of the printed image or even its destruction cannot with certainty be excluded.
SUMMARY OF THE INVENTION
The invention is based on the object of indicating a system and a process for avoiding slip in the transport of a recording substrate in a fixing station of an electrographic printer or copier with the aid of which the occurrence of slip between the recording substrate on the one hand and the fixing roller and/or the nip roller on the other hand can be counteracted.
This problem is solved using the features specified in patent claims 1 and 7. Advantageous refinements and deve
REFERENCES:
patent: 4147922 (1979-04-01), Naeser et al.
patent: 4513898 (1985-04-01), Spitsbergen
Patent Abstracts of Japan, vol. 5, No. 206, (M-104), 26 Dec. 1981, Tension Controller for Long-scale Sheet, T. Tsutomu, JP 56 122758 dated 26 Sep. 1981.
IBM Technical Bulletin, vol. 35, No. 4B, dated Sep. 1992, Continuous Forms Output Buffer, pp. 436-439.
F & M Feinwerktechnik & Messtechnik, vol. 100, No. 8, dated Aug. 1992, Praezise Gesteuerte Schrittmotoren Ermoeglichen Rueckseitendruck, K. Mayer, pp. 339-343.
Kreiter Alexander
Kremastiotis Vassilis
Grainger Quana
Grimley Arthur T.
Oce Printing Systems GmbH
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