US2879127A - Apparatus for electrical recording in telephoto systems - Google Patents

Description

March 24, 1959 H. CARLSON APPARATUS FOR ELECTRICAL RECORDING IN TELEPHOTO SYSTEMS Filed Aug. 29. 1956 United States Patent APPARATUS FOR ELECTRICAL RECORDING IN TELEPHOTO SYSTEMS Harold Carlson, Eastchester, N.Y.

Application August 29, 1956, Serial No. 606,894 4 Claims. (Cl. 346-74) This invention relates to electrical recording for facsimile and telephotography, and more particularly to a method and apparatus for insuring uniform, high-quality recording where the electrolytic marking process is employed.

In electrolytic recording, use is made of a porous record member or sheet moistened with an electrically conductive aqueous solution. A great many different types of recording paper of this class have been proposed in which a discoloration reaction is produced on the passage of electric current. An essential requirement of satisfactory recording material for photo transmission is that a clear mark of high definition with a minimum of fringes shall be made with a comparatively weak current, both the mark and the background being stable in appearance for a reasonabletime.

Currently electrolytic paper is available having the desired characteristics of adequate tone range and stability. These optimum and distinctive recording characteristics however are only obtainable when the moisture content of the paper is maintained within about 0.5 percent of the optimum value, and this appears to be true of all commercially available papers. Furthermore the distribution of moisture must be uniform in the recording areas. In practice it has been diflicult to maintain the desired amount and distribution of moisture in the paper during manufacture and up to the point of actual recording. This has greatly restricted the use of electrolytic recording material where reproduction or recording of high quality is desired.

3 The object of the invention, in general terms, is to provide an improved method and apparatus for obtaining high-quality, sharp recording bythe electrolytic process under the extreme conditions of ambient temperature and humidity which heretofore caused degradation of the copy.

Another object of the invention is to increase the range of moisture content in the recording medium and/ of the non-uniform distribution thereof which may be tolerated, without degrading the quality of reproduction.

The efiectof a slight change in moisture content upon the recording quality is so objectionable that many attempts have been made to overcome the problem, as for example, by sealing the paper in a moisture-proof container until used and then recording on the sheet in a hermetically sealed cabinet (sealed except where the recorded web passed through a delivery slot in the cabinet) This is costly and inconvenient, and since it does not prevent deterioration of recording quality under lowhumidity amibient conditions, is not a practical solution to the problem. 7 I have found that the low humidity frequently encountered in dry areas, as in Arizona or Denver, Colorado, and also in heated otfices in the wintertime, causes pronounced degradation in the recordingeven where sealed as described. This appears tobe due to the porous character of the base paper which acts like a wick to draw moisture rapidly from 2,879,127 Patented Mar. 24, 1959 ICC the moist trailing section of the paper to the dry recorded area, and thus reduce the moisture content at the recording area below that necessary for the desired recording quality.

Another suggestion that has been made is to impregnate the paper with the solutions and marking materials on the recording machine just before it is to be used. This greatly increases the cost and complexity of the recording equipment, and a highly skilled, technically trained operator is required. The coating apparatus would normally be adjusted to apply an excess of coating solution and automatically controlled means would be used to reduce the moisture to the correct amount, as by heating the web after impregnation. It is extremely difficult to maintain the desired moisture content in this manner. Furthermore the capillary action of the drier recorded area upon the unrecorded trailing area of the paper would cause degradation of the recording under low-humidity ambient conditions in the room where the recorder is operating.

Another object of the invention therefore is to provide a simpler and more effective solution for this problem, which does not involve any regulated heating or moistening equipment, humidity controls and the like.

Other objects and advantages of the invention will appear from the following description of the preferred embodiment shown in the accompanying drawings, in which:

Fig. l is a perspective view of an electrolytic recorder having the moisture-control unit embodying the invention mounted on the front thereof;

Fig. 2 is a diagrammatic view showing a preferred arrangement of paper feeding, recording and moisture-control elements, adaptable to a recorder such as that shown in Fig. 1; and

Figs. 3, 4 and 5 are detail views of the parts of the moisture-control unit and a typical mounting flange therefor.

Referring to Fig. 1, a recorder of the electrolytic type is shown by way of example, consisting of an outer casing or cabinet 10 having a hinged front cover section 11. This cover section is hinged at the bottom edge so that it may be swung open for convenience in loading the recorder. The construction of the recorder shown is conventional except as hereinafter noted and only sufiicient details are illustrated as are necessary to explain the invention.

The recorder is adapted to use electrolytic paper consisting of a sheet moistened with an electrically conductive aqueous solution of the type well known in the art. The recording sheet or paper 12 as shown is fed from a supply roll 14 over the helix drum 15 which forms a part of the recording mechanism. A take-up roll 16 or equivalent for support of the paper may be provided on the outside of the cabinet. Any suitable means may be provided for supporting and feeding the paper. The casing or cabinet is ordinarily closed or adequately sealed to prevent rapid drying out of the recording sheet but is not necessarily hermetically sealed or completely sealed in a moisture-proof manner. This would not be possible, for example, where the record member 12 is fed through a slot 18 in the casing or cabinet, as shown.

In accordance with the invention, moisture-control means, indicated generally at 19, is provided adjacent the recording area and for convenience may be mounted as shown on the cover section 11 of the cabinet. The detailed construction and operation of this unit will be explained in connection with Fig. 2 and a typical unit is shown in Figs. 3 and 4 by way of example.

Referring to Fig. 2, the recording arrangement according to the invention is illustrated in this figure using the same or corresponding reference numbers as used in Fig. l. The slot 18 in the cabinet through which the record member 12 is fed may include feed rollers 21 as shown. However such members do not provide a complete seal and in the case of low humidity ambient conditions it is found that the recording quality rapidly deteriorates With this conventional arrangement. As already explained this results from the fact that a very slight change in the moisture content of the paper 12 is sufiicient to degrade the recording. If the paper is too moist, the recording mark runs or blots so that the recording is blurred. If the recording medium is slightly drier than the optimum moisture content, the density of the recording mark fades and the paper is also burned by the recording current. The burning is evidenced by the tearing of the sheet by the recording helix where it has become weakened by the burning action. Thus the drying out of the paper cannot be tolerated even if the washed-out appearance of the recording is acceptable.

Drying out of the record sheet or member 12 is found to be principally due to causes other than the leakage of moisture from the interior of the cabinet, since it would appear that this could be compensated for or corrected by placing sponges or water receptacles at random inside the paper compartment. This has proved unsatisfactory and impractical. The principal reason for the drying out of the paper to the point where the recording is unsatisfactory when the recorder is used under conditions of low humidity is that the drying out of the paper as it feeds out and is exposed to dry air, aided by the drying effect of a heated bar sometimes used to smooth the paper, causes the porous sheet to act like a wick and draw moisture from the unrecorded area. Thus when the unrecorded portion of the sheet reaches the recording mechanism, the surface of the sheet has lost enough moisture to adversely affect the recording quality.

The recording mechanism in a typical recorder consists of a helix drum 15 and a writing blade 22 between which the electrolytic paper passes and is fed at a uniform rate. The Writing blade 22 may be carried by the hinged section 11 and rests in contact with the surface of the recording sheet when the cover is closed. The edge of the writing blade must rest with a uniform pressure across the Width of the recording sheet and the marking potential is applied to the sheet by the helix and writing blade.

In accordance with the invention, a moisture control unit consisting of a fibrous block of porous material 23 containing water is provided adjacent to the recording area and closely spaced from the recording surface of the paper. This block or piece of fibrous material 23 is mounted in a position to provide a moist stratum coextensive with the width of the recording area and adapted to continuously furnish a controlled amount of moisture to the sheet or member 12 at or near the recording area. Thus the control unit may consist of a block of compacted fibrous material such as wool felt, mounted in a hollow holder 24, shown in Fig. 4. The fibrous material such as wool felt contains many capillary openings which will hold water and gradually release moisture ata controlled rate over a period of several hours or more. Other organic spongy or fibrous materials may be used with some success, but best and most practical results are obtained with a dense wicking type felt as compared with ordinary coarse sponges or loosely woven or compacted materials.

While the theory of operation of the moisture control method described is not fully understood, since very little moisture is removed from the felt in obtaining satisfactory control of the recording characteristics, it is believed that the drying from wicking action of the paper is most rapid at the surface and has the maximum effect on the recording where there is a deficiency of moisture at this point. Thus the increase in moisture on the surface of the record sheet supplied by the stratum right at this point appears to have an usually beneficial effect since the use of pans of water and the like inside 4 the paper compartment have been found totally ineffective. In fact, the uncontrolled moistening action resulting from the use of such pans is objectionable in ordinary day-by-day operation because of the tendency to produce Wet spots or even widespread wetting of the paper with consequent blurred recording.

The moisture control unit according to the invention has the further advantage that paper which by reason of manufacturing difiiculties or long storage on the shelf is slightly low in moisture content can be used with satisfactory recording results. This is an important advantage as it decreases the cost of manufacture as well as saving the cost of defective rolls on the users shelves,

' since these rolls cannot be remoistened or reconditioned and have to be thrown away. On the other hand, the moisture control according to the invention does not produce excessive moistening under ambient conditions of ordinary or relatively high humidity, but instead improves the recording under these conditions also. A perceptible graininess in the recording, apparently due to incomplete saturation of the individual paper fibres, is reduced by the controlled moisture treatment.

For convenience the moisture control unit consisting of the block of felt 23 and the holder 24 may be removably held on the front cover by means of a slotted bracket 25. The bracket 25 as shown is provided with a bottom slot 26 and slots 27 and 28 on the sides to receive the edges of the holder 24 and provide a reasonably tight air seal for the cabinet. The moisture control unit 23, 24 is simply lifted out of the bracket 25 whenever it has to be replaced with a new unit containing a saturated felt.

When the preferred heavy felt material, such as American Felt Company No. 51018 medium density wicking felt, is used in the control unit, replacement need not be made oftener than once a day even under exceptionally dry ambient conditions. Under usual lowhumidity conditions in dry localities, a one-inch block of this dense felt does not dry out to the point where it is unusable in less than 24 hours. 7

In a typical installation in a hot, dry climate, the block of 51018 felt used contained water weighing nearly six times the dry weight (94 grams) of the felt when saturated. The loss of water in use was substantially constant for hours at the rate of about 1 to 2%, and sur prisingly enough this rate of emission is afiected little if at all by temperature changes and by changes in relative humidity of the ambient atmosphere between 7 and 35%. The block of felt measured 11% x 1% x 1 inch and the exposed face was spaced about 1 inch from the opposed recording surface. This spacing is somewhat critical and excessive spacing, more than a couple of inches, should be avoided in recorders of the type described, although some improvement is obtained of course even with greater spacing.

Various modifications of the embodiment of the invention described above will occur to those skilled in the art and may be made without departing from the scope of the invention.

What is claimed is:

1. In an electrolytic photo recorder having an outer casing or cabinet, in combination, means for supporting an electrosensitive paper supply roll in said casing or cabinet, recording means, means for feeding the electrosensitive paper past the recording means to record thereon in accordance with signals impressed upon the recorder, said paper being of the type which is deleteriously affected in its recording characteristics by comparatively small changes in its moisture content, and means for enhancing the recording quality comprising a moist stratum disposed inside said casing or cabinet adjacent the recording area on the paper, spaced from the surface of the paper and substantially coextensive with the width of said recording area.

2. A recorder as claimed in claim 1, in which said moist stratum is composed of the exposed surface of a fibrous material containing many capillary openings from which controlled evaporation takes place.

3. A recorder as claimed in claim 1, in which said moist stratum is composed of wetted compacted fibres such as wool felt. I

4. In an electrolytic photo recorder, in combination, recording means including a helix drum and cooperating writing blade, means for feeding electrolytic paper or specified moisture content between said helix drum and writing blade, a hinged support for said writing blade whereby the blade can be separated from the helix drum for reloading the paper, the recording process partially References Cited in the file of this patent UNITED STATES PATENTS 2,127,331 Fulton Aug. 16, 1938 2,427,611 Lane Sept. 16, 1947 2,480,890 Tribble Sept. 6, 1949 2,624,652 Carlson Jan. 6, 1953 2,680,056 Olden June 1, 1954

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