` ~0~79a This invention relates to an improved device and method for measuring the nip or contact arc characteristics of pressure heated fusing rolls as are used in electrostatic reproduction systems.
It has been recognized that one of the preferred ~;
ways for fusing a powder image to a substrate is to bring ; -the powder into direct contact with a hot surface, such as `
a heated roller. The roller surface may be dry, i.e., no application of a liquid release agent to the surface of that roller as described, for example, in U. S~ Patent Nos. 3,4g8,596, 3,539,161 and 3,666,2~7. Alternatively, the fuser roll surface may be melted with a release agent such as silicone oil as -- described in U. S. Patent Nos. 3,268,351 and 3,256,002.
It has been found that the measurement of the contact arc and the pressure in the nip of the rolls is desirable from the standpoint of adjusting the nip to obtain high quality fixing of co W sheets. Therefore, the ease with which these parameters can be immediately ascertained under varying conditions can be extremely advantageous in the set up of a machine in the minimum time.
The present invention is for a method and device for rapidly ascertaining the pressure and contact arc of the nip formed by pressure fusing rolls used in reproduction machines. This is accomplished, generally speaking, by off-setting a portion of a toner pattern from a strip onto another strip for immediate analysis. The present invention is par~
ticularly intended to be an improvement over U. S. Patent 3,861,219 issued January 21, 1975 and commonly assigned.
Now, and in accordance with the present teachings, there is provided a means for measuring heat and pressure of a .'' ~ '''' .
fusing nip between heat and pressure fusing rolls. A sheet of polyimide film material having a coating of silicone rubber material of a thickness ranging from about .002 to about .004 inches is positioned in overlying re:Lationship with a transparent sheet of polyimide film material hav:ing a thickness in the range of about .003 to about .008 inches. The sheets are passed through a nip means whereby pressure is applied for a predetermined time and the sheets subsequently removed from the roll having an indication of the pressure and contact arc characteristics of the nip.
Various aspects of the invention and further features thereof will be better understood upon reference to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:
Figure 1 illustrates schematically a xerographic reproducing apparatus incorporating a heated pressure fuser roll apparatus to be measured in accordance with the present invention; , Figures 2a and 2b are side views of the fusing rolls ~`~
illustrating the measurement steps in sequence~
Figure 3 is an enlarged portion of the device of the invention after measuring pressure and contact arc characteristics of' and Figure 4 is a view similar to Figure 3 illustrating the separation of the sheets of the device to remove a character-istic pattern thereon.
Referring now to the drawings, there is shown in Figure 1 an automatic xerographic reproducing machine incor-~ 30 porating heat and pres~ure fusing rolls to be measured according to the invention. The automatic xerographic reproducing machine - ~ ' - ~ .
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includes a xerographic plate or surface 10 formed in the shape of a drum. The plate has a photoconductive layer or light receiving surface on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow.
The rotation will cause the plate surface to sequentially pass a series of xerographic processing stations. For the purpose of the present disclosure the several xerographic processing stations in the path of movement of the plate -surface may be described functionally as follows:
A charging station A at which a uniform electro-static charge is deposited on the photoconductive plate;
An exposure station B, at which light or a radiation pattern of copies to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image on the copy to be reproduced;
A developing station C, at which xerographic developing material, including toner particles having an ele~trostatic charge opposite that of the latent electro static image to form a toner powder image in configuration of the copy being reproduced;
A transfer station D at which the toner powder - image is electrostatically transferred from the plate surface to a transfer material or a support surface mode of paper;
A drum cleaning and discharge station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and at which the plate is exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon, and , -~L0~7~(1 A fusing station F at which the toner powder image is affixed to the paper support material by fusing rolls 103 and 105 which apply heat and pressure.
~ The processing description of the xerographic process is sufficient for an understanding of the instant invention. Further details may be had by reference to U. S. Patent No. 3,578,859 filed July 3, 1969, and commonly assigned herewith.
In accordance with the invention the quality of the copies provided by the machine is affected by the fusing characteristics at the nip formed fuser roll 103 and pressure ' roll 105 through the copy sheet to be fused is advanced.
The fusing rolls may be wetted or dry as described above. In either case the nip pressure and heat are critical in obtaining high quality fusing. For the dry system the fuser roll comprises a rotating member 130 having an elastic compressible coating 132 made of silicone rubber or any suitable ~ii heat resistant compressible materlal as described, for example, in the aforementioned patents. The rotating member may intern-¦ 20 ally heated by a heat source 134 as described in U. S. Patent ¦ No. 3,666,247 or externally heated as described in UO S. Patent ~- ~os. 3,498,596 and 3,539,161. The pressure roll comprises a S rotating member 140 which is covered with an elastic layer 142 of a slightly higher durometer than the fuser roll coating 132 ¦ 25 as described in the aforementioned patents. The subject j invention is concerned with the immediate determination of the heat and pressure characteristics of the nip.
Referring specifically to Figures 2a and 2b there is shown the steps ~or measuring the contact arc or nip ¦ 30 formed by the fusing rollers. The measurement device 200 ~ . , ' ' . .
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comprises two sheets 201 and 210 which are made of a polyimide `
material and which have a thickness ranging from about .003 to about .008 inches. A preferred sheet material is manu- -factured under the trademark Kapton by DuPont Corporation, -5 Wilmington, Delaware. Sheet 210 has a coating 215 which is , . ; ~
made of silicone rubber which has a thickness of about .002 to about .004 inches. Suitable coating materials are manufactured by General Electric Co. under the tradenames 100, 108, 112 and 102 by Dow Corning under the tradenames 236 and 735 and combinations thereof. Sheets 201 and 210 are inserted between the fusing rollers 103 and 105 while the rollers are separated. ~ext the fusing rollers are closed to form an operating nip for a predetermined time. Preferably this time ranges from about five to about seven seconds. In the final step the fusing rollers are removed from each other to an inoperative position and the sheets 201 and 210 removed.
It has been observed that sheet 201 will have a distinct impression formed from the silicone rubber coating 215. As understood the elastom~ric coating when under compression stretches and provides intimate contact with the surface in contact therewith. The surface is held into contact with the elastomeric coating after release of the pressure of the nip --due to electrostatic surface forces. Sheet 201 is transparent -enabling instant detection of the nip characteristics, such as, contact arc width with the human eye. Upon separation of the sheets the impression is removed for reuse of the device.
The operation of the measuring device is best understood from Figures 3 and 4. In Figure 3 the width of the impression pattern 220 is used to determine the contact arc width of the fusing rollers. Thus if there is too much pressure there will be an increase over the standard nip width ...
~ -6-~4~:790 normally observed for the machine operation conditions. On the other hand, if there is insufficient pressure in the nip the width will be decreased from the standard~
Furthermore, it will be observed that since the materials of the device are heat stable there is no effect from the high temperatures associated with pressure heated fusing rollers. Upon separation of the sheets the impression disappears as best shown in Figure 4. In this manner the ` device can be used over and over again until optimum conditions are observed.
- It will now be appreciated that by observing the pattern 220 it is possible to determine immediately the pressure characteristics of the nip formed by the fusing rolls.
With this in mind the pressure and contact arc of the nip can be adjusted and the tests easily repeated until the desired operating conditions are obtained. The pattern will not fade and is reusable if desired.
While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated ana in its operation may be made by th~se skilled in the art without departing from the spirit of the invention.