US2541416A - Heated drying roller - Google Patents

Description

Feb. 13, 1951 H. HARRISON HEATED DRYING ROLLER Filed July 26, 1947 FIG. 4.

FIG.3.

FIG. 5.

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W (H 0 Z w rins :the drum and "heating means Patented Feb. 13, 1951 HEATED DRYING ROLLER Henry Harrison, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 26, 1947, Serial No. 763,923

3 Claims. 1

The present invention relates to drying drums for'rollers, and more particularly to a heating means therefor.

Drying drums used for drying photographic prints are large and slow urning, and are difflcult to make since they are usually formed of extruded copper to avoid joints. Such drums are subjected to corrosion when heated with water or steam. In order to avoid such corrosion, some drums are heated by electric coils or similar means positioned within the drum. Such heating arrangements do not however provide a uniform heating of the drum, and the heating means themselves are high-temperature units, the disadvantage of which will be readily apparent to those in the art.

' In order to overcome these disadvantages, the present invention provides a drum which is formed of a material having a high magnetic permeability. A means is provided for producing a low-frequency magnetic flux, and this means is linked with the drum to provide a magnetic flux path of low reluctance. This flux produce hysteresis and eddy current losses which serve to heat the drum uniformly and to the desired temperature and without the use of high-temperature heating means.

f'yThe present invention has, therefore, as its in which the coil only is used and the drum con- I stitutes theentire flux path; and

principal object the provision of an arrangement for heating a drying drum by means of hysteresis and eddy current losses.

"A further object of the invention is the provision of an arrangement in which the drum itself forms part ofthe magnetic flux path.

" -Yet another object of the invention is the use I of a low-frequency alternating magnetic flux for heating the-drum.

Still another object of the invention is the provision of an arrangement for heating the drying drum which is simple, and which does not employ high-temperature heating means.

To these and other ends, the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specification.

In the drawings:

1;, Fig. Iris a transverse vertical sectional view through a drying drum, showing one embodiment of a heating means constructed in accord- ;ance with the present invention;

Fig. 2 is a longitudinal sectional view through illustrated in Fig.

"1 on line 2-2 thereof;

Fig. 3 is a perspective view of the drum and core illustrated in Figs. 1 and 2 with part of the dr-u-m-broken away to show more clearly the arrangement of the parts;

Fig. 4 is a vertical sectional view showing a modified arrangement of drum and heating coil Fig. 5 is a sectional view through the drumand coil illustrated in Fig. 4 and on line 5"-5 thereof showing the relation of the parts.

Similar reference numerals throughout thevarious views indicate the same parts.

The present invention relates to an arrange ment which utilizes hysteresis and eddy current losses for heating a drying drum. To secure this result, a drum is formed of a material having a high magnetic permeability and has posi-' tioned therein a laminated core which is'linked to the drum to provide a flux path of low reluctance. A low-frequency alternating current is supplied to a coil associated with the core to produce an alternating magnetic flux in the flux path through the core and drum. The core is laminated so that the losses occur principally in the drum rather than in the core so as to eifectively heat the drum uniformly and without the use of high-temperature heating elements.

Figs. 1 to 3 show one embodiment of the invention in which is provided a novel print drying drum l'l formed of a material of high magnetic permeability, such as unannealed but stress-relieved cast iron, cold. rolled steel, or high carbon steel. The drum is supported on a pair of rollers l2 one of which may be driven to rotate the drum at the desired speed. Suit able aprons, not shown in Figs. 1 and 3, cooperate with the drum to hold the print in contact therewith during the drying operation. If desired, the drum may be provided with a suitable coating, such as copper (chromium-plated).

A laminated iron core which in the present instance is H-shaped, is provided with spaced legs l3 and I4 which are positioned adjacent the inner surface of the drum, and a cross or connecting member I5 on which is positioned a winding or coil l5 adapted to be connected to a source of low-frequency alternating current, not shown. By low frequency is meant frequency below cycles per second. As the core and drum are iron, and the air spaces between the legs I3 and i4 and the drum are quite small, the core forms with the drum a magnetic flux path of low reluctance. When low-ire quency alternating current is applied to the winding l5, an alternating magnetic flux is produced in the magnetic flux path through the core and drum. As the same flux passes both through the core and drum, the cross-sectional area of the core is equal to the area of the drum carrying the fluxnamely, the drum -length multiplied by twice the drum thickness.

The alternating magnetic flux in the flux path gives rise to hysteresis and eddy current losses, the latter of which are larger.- These losses cause a heating action to take place, and as the core is laminated, the losses occur principally in the drum so that the heat resulting from such losses is utilized to heat the drum to the proper temperature. As the drum itself forms part of the magnetic flux path, the heating resulting from such losses serves to heat the drum uniformly. The actual amount of power necessary to heat the drum to the desired temperature will vary with the size and composition of the drum, but with a cast iron drum 4' in diameter and 24" long and A;" thick, 5000 watts are required. This, however, is about the maximum power which can be delivered at 60 cycles to a drum of this size.

As the major part of the losses occur directly in the material of the drum, substantially all the heat resulting from such losses is utilized for heating the drum. Also the heating is produced without the use of high-temperature r corroding heating means, and the structure is extremely simple. The core and the winding may be carried by end plates, not shown, which close the end of the drum. These plates are preferably stationary so that the core and winding remain in fixed position within the drum.

While the core as shown is H-shaped, other shapes, such as U-shaped cores, may be used. The fundamental requirement is that the core form with the drum a magnetic flux path of low reluctance. While the use of a core is preferred, the core may be eliminated but the winding or coil which provides a magneto-motive force must be linked with the iron flux path of the drum. In the arrangement in Figs. 1 to 3, the drum itself forms only a part of the flux path, but in the embodiment shown in Figs. 5 and 6, the drum constitutes the entire flux path.

In this latter arrangement, the drum H has wound therearound a hollow winding or core through which a portion of the drum extends and moves so that the drum will constitute a core for the winding. The latter is connected to 110-volt, 60-cycle source of power and when the latter is applied to the coil 20 an alternating magnetic flux is induced in the drum which now forms the complete flux path. As in a previously discussed arrangement, illustrated in Figs. 1 and 3, this alternating magnetic flux causes hysteresis and eddy current losses to develop in the drum and these losses serve to heat the drum to the proper temperature. Parts in Figs. 4 and 5 which correspond to those in Figs. 1 to 3 are designated by the same numerals.

Thus in both embodiments, the drum itself forms a portion at least of the magnetic flux path, and when the path is subjected to a low frequency alternating magnetic flux, hysteresis and eddy current losses result and these losses are utilized directly to heat the drum. Such heating means is low temperature and produces a uniform heating of the drum.

While certain embodiments of the invention have been disclosed, it is to be understood that the inventive idea may be carried out in a number of ways. This application is, therefore, not to be limited to the precise details described, but is intended to cover all variations and modifications thereof falling within the scope of the appended claims.

What I claim is:

'1. A drying apparatus comprising, in combination, a rotatably mounted cylindrical drum formed of a material of high magnetic permeability, a stationary laminated core of high magnetic permeability positioned radially within said drum in inductive relation therewith and having portions thereof commensurate in length with said drum, said portions being positioned adjacent but physically disconnected from said drum, an electrically conducting coil positioned on another portion of said core and supplied directly with low frequency alternating current of at least volts potential, the flow of current through said coil producing magnetic flux in a low reluctance path a part of which is in the core in a direction radially of said drum and another part of which is in a circumferential direction through said drum.

2. Drying apparatus comprising, in combination, a rotating hollow drum having a cylindrical portion formed of a material of high magnetic permeability, an H-shaped laminated stationary core of high magnetic permeability positioned radially of said drum in inductive relation there.- with and having legs extending axially of and commensurate in length with said drum, said legs being position adjacent but spaced slightly from and disconnected physically from said drum, a cross-member extending radially of said drum and connecting said legs, a coil wound on said cross-member and supplied directly with low frequency alternating current of at least 110 volts potential to set up magnetic flux in two independent and separate low reluctance paths both of which are through the laminated core and each of which is in a circumferential direction through the cylindrical portion of said drum. 1

3. A drying apparatus comprising, in combination, an H-shaped laminated core of high magnetic permeability, an electrically conducting coil wound on the cross arm of said core, a rotating hollow drum having a cylindrical portion closely surrounding said core in inductive relation therewith and with the axis of the drum parallel to the laterals of the H, and the drum immediately adjacent said laterals, said drum being formed of a material of high magnetic permeability and having approximately the same length as said laterals, said coil being supplied directly with low frequency alternating current of at least 110 volts potential, the flow of current through said coil setting up magnetic flux in said core the return path of which is in a circumferential direction through the cylindrical portion of said drum.

HENRY HARRISON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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