US3621201A

US3621201A - Developer apparatus for heat developing paper

Info

Publication number: US3621201A
Application number: US819066A
Authority: US
Inventors: Paul J Crane; Glenn A Reese
Original assignee: Magnavox Co
Current assignee: Philips North America LLC
Priority date: 1969-04-24
Filing date: 1969-04-24
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

An image developer for heat developing paper, such as dry silver paper, wherein a curved platen is heated by passing a current therethrough, thereby obtaining very quick heating time and very uniform heat. A belt means, such as a fabric belt, is held by rollers snugly against the platen surface that is heated, and the belt is driven by connecting the rollers to a motor and the paper to be developed is inserted between the fabric belt and the platen and caused to move about the heated platen, thereby providing ''''averaging'''' the heat to the paper.

Description

United States Patent [72] Inventors PaulJ.Crane Torrance; Glenn A. Reese, San Pedro, both of Calif. [21] Appl. No. 819,066 (22] Filed Apr. 24, 1969 [45] Patented Nov. 16, 1971 [73] Assignee The Magnavox Company Fort Wayne, Ind.

[54] DEVELOPER APPARATUS FOR HEAT DEVELOPING PAPER 7 Claims, 6 Drawing Figs.

[52] U.S. C1 219/388, 34/151, 34/164, 219/243, 219/541, 219/469, 219/494 [51 Int. Cl F271) 9/06 [50] Field of Search 219/216,

[ 5 6] References Cited UNITED STATES PATENTS 2,569,773 10/1951 Orr 219/543 2,977,450 3/1961 Boicey 219/541 3,302,002 1/1967 Warren 219/543 3,506,804 4/1970 Schippers et al. 219/388 2,532,562 12/1950 Lorig 219/469 2,629,808 2/1952 Ulmschneider. 219/243 2,557,983 6/1951 Linder 219/543 2,939,223 6/1960 Smith 34/58 3,113,198 12/1963 Shinn 219/243 X 3,294,947 12/1966 Whitmore 219/469 X 3,449,547 6/1969 Goodman et al. 219/216 Primary Examiner- Volodymyr Y. Mayewsky A!!0rnt \X-Jffl8 and Young and Richard T. Seeger ABSTRACT: An image developer for heat developing paper, such as dry silver paper, wherein a curved platen is heated by passing a current therethrough, thereby obtaining very quick heating time and very uniform heat. A belt means, such as a fabric belt, is held by rollers snugly against the platen surface that is heated, and the belt is driven by connecting the rollers to a motor and the paper to be developed is inserted between the fabric belt and the platen and caused to move about the heated platen, thereby providing averaging" the heat to the paper.

PATENTEuuuv 16 197i 3, 621 .201

sum 1 or 3 F l TEMP. CONT L H5 All SERVO FIG IA INVENTORS QLENM REE: PAUL CRANE PAFENTEDRQ 5: 3.6 21,2 01

SHEET 2 OF 3 F|G.3 DEVELOPER CONTROL TEMPERATURE CIRCUIT 56 '58 54 EMA LINE n VOLTAGE 2., 2N2000 30o ZENER 22v 66 is, m 60 ZNIGH I25 1 sun PATENTEBNUV 16 I97] 6* 1'". 1'

SHEET 3 [1F 3 PAPER 961 lNSERTlON INVENTORS GLENN A. QEESE AUL J. CRANE HQWHAQDT. SEEGER Aflorney DEVELOPER APPARATUS FOR HEAT DEVELOPING I PAPER One of the major problems in previous devices for developing previously exposed heat-sensitive paper, such as dry silver paper, was the inability to provide a unit which would quickly heat to the necessary temperature and which would provide uniform heat to the entire surface of the paper. Quick heating is necessary since many developing machines are not continually used and therefore it is impractical to keep the developer turned on continuously since this not only wastes power but tended to burn out the heating elements in the developer. However, in previous devices it took relatively long periods of time to raise the developing device to the proper temperature and a further period of time to insure that the developer surface was of uniform temperature. Uniform temperature is needed since otherwise the paper which is developed will have streaks and spots corresponding to the nonuniform heating of the developer.

Previous devices relied primarily on a plurality of small resistive devices insulated from one another and also insulated from a metallic surface for heating the paper in the developer. In order to heat the surface in the developer, it was necessary for the heat from the resistive elements to be transferred to the surface and an additional period of time was necessary until the heat alongthe surface of the developer had sufficient time to flow across the surface of the developer had sufficient time to flow across the surface to obtain a uniform temperature.

This invention overcomes these deficiencies by providing a platenthat is heated directly by the power source. This not only reduces significantly the time that it takes for the platen to reach the temperature needed for developing but since the platen itself is being heated, by having the current flow therethrough, the temperature in the platen surface is at all times uniform, thereby making unnecessary a long waiting time to obtain unifonnity of temperature.

It is therefore an object of this invention to improve and advance the art in image developers using heat-sensitive paper, such as dry silver paper, to widely increase the use of such developing techniques.

Another object of this invention is to provide a heating platen in a developer of the kind referred to above that has current passing directly therethrough for reduced heating time and uniformity of surface heat.

It is a further object of this invention to cause the paper to move relative to the surface of the heated platen and to keep the paper in close contact therewith to further improve upon the uniformity of the heating of the paper.

Another object of this invention is to provide means for maintaining the paper in close contact with the platen by having a belt driven over the platen and by inserting the paper between the belt and the platen. Means are provided to cause the belt to be agitated or moved relative to the paper as it carries the paper over the platen so that any high spots on the belt will be averaged over an area of the paper, thereby further improving uniformity of heating of the paper.

Another object of this invention is to provide a polished platen to facilitate uniform movement of the paper over the platen, improve heat transfer from the platen to the paper, and to improve uniformity of heating of the paper.

These and other objects of this invention will become more apparent when a specific embodiment is considered in connection with the following drawings:

FIG. 1 is a perspective, schematic view of a preferred embodiment of this invention;

FIG. 1A is a sectional view of an embodiment of this invention where the platen'has notched ends to control the temperature of the platen at the ends thereof;

FIG. 2 is a perspective, schematic view of the paper drive of FIG. -I and is shown separately for clarity;

FIG. 3 paper heating mechanism, is a schematic circuit diagram of means for maintaining the surface of the platen at a predetermined temperature;

FIG. 4 is a plan view of the belt paper drive wherein the belt drive rollers are mounted eccentrically; and

FIG. 5 Is a section taken at $--5 of the paper drive of FIG. 4.

In FIG. 1 is shown a resistive element heating platen 20 which may be ten-thousandths of an inch thick and may be of a light gauge inconel or nichrome. Plate'n 20 is a truncated drum and has attached at each end a conductive end plate 22 which may be of copper or other highly conductive material. For certain applications platen 20 may be coated with a plastic such as "Teflon" or other similar material.

Attached to copper end plates is a metallic strap 24 which also may be of copper and which passes through the central opening of transformer core 26. The primary winding 28 of transformer core 26 has a very large number of turns compared with the secondary winding which is shown as a single turn but may be more than one tum and comprises strap 24, end plate 22, and platen 20. The primary is connected to temperature servocontrol 28 which will be later described.

The ends of platen 20 may have notches 30 as shown in FIG. 3. The purpose of placing notches 30 at the ends of platen 20 is to increase the current flow in the legs 32 of the notches, thereby raising the temperature of these legs in comparison with the surface of platen 20 to compensate for the normal cooling that the edges would have.

PAPER DRIVE MECHANISM The paper drive mechanism is shown in FIG. 2 where platen 20 has been removed from its power source for clarity. In this embodiment the platen 20 is stationary while rollers 34, 36 are placed below the platen and

rollers

38, 40 are placed above the platen with an endless cloth belt 42 wrapped tightly about the platen surface and then around the outside of the

rollers

34, 36, 38, and 40, which are mounted for rotation about their axes. (The supports for the axes are not shown.) Rollers 34 and 36 are driven by belt 44 which in turn is driven by motor 46.

Attached to lower edges of platen 20 are guides 48, 49. If drive motor 46 is in the on" condition, the placement of paper 50 on guide 48 between belt 42 and platen 20 will cause the paper to become engaged between the belt 42 and the platen 20 to carry the paper around the platen 20 as the belt is driven by motor 46. The paper 50 may be placed with emulsion side against platen 20 or, if the emulsion tends to stick to platen 20, it may be placed with emulsion side away from platen 20. This insures unifonnity of heating of the dry silver paper since if there are any unevenly heated areas of platen 20 due to defects in the platen surface, there will be a tendency to average" these nonuniform areas with the other areas of platen 20.

When power is supplied to primary 28, a large current is developed through strap 24, end plates 22, and platen 20. This will bring the temperature of platen 20 quickly and uniformly to developing temperature, thereby providing an improved device. Servo Temperature Control CircuitA temperature control circuit such as shown in FIG. 3 may be used to maintain the temperature of platen 20 at a constant level. The specific structure shown is known to the art but will be briefly described thereof. A temperature sensor 52 of the thermistor type is placed on the underside of platen 20 and is in contact therewith to sense the temperature, and thermistor S2 is connected as indicated in circuit of FIG. 3. Line voltage 54 is applied to a full wave rectifier 56 through a transformer 58 to supply a voltage to voltage divider circuit which supplies a pulse to transformer 60 with the pulses having a frequency similar to that of the line voltage frequency but having a period, or time per pulse that the energy is applied inversely, proportional to the temperature of thermistor 52; the cooler the thermistor 52, the longer the period, and the warmer the thermistor, the shorter the period. The purpose of this type of circuit is to provide a circuit that is extremely responsive to the thermistor temperature.

The manner in which the thermistor controls the pulse periods will now be described. Thermistor 52 controls the outut of transistor 62 which in turn charges a capacitor 64 and when capacitor 64 voltage reaches a predetermined level, a unijunction transistor 66 turns on immediately. Unijunction transistors are very responsive to voltage level and react almost instantaneously to a given voltage level.

Transistor 66 stays on until the instantaneous line voltage goes through zero, at which time it turns off. The pulse applied by transistor 66 is passed through the primary 68 of transformer 60 and the

secondaries

70 and 72 of transformer 60 are connected through SCR devices 74 and 76 respectively to the primary 28 of the heater circuit shown in FIG. 1. The SCRs 74 and 76 are connected so that one of them will fire regardless of the polarity of line voltage 54. A neon light 78 is connected across primary 28 and glows according to the current being applied to primary 28 so that at any time it is possible to tell visually whether the platen 20 is being charged and to what extent. if the thermistor S2 is relatively cool, then the on time of transistor 62 will be larger whereas if the thermistor S2 is relatively warm and above the predetermined temperature then the on time of transistor 62 will be shorter, thereby keeping the power applied to the primary 28 and platen 20 at the proper level to maintain a given temperature.

FIG. 4 shows only the paper drive for the embodiment shown in this invention.

Belt 80 is driven by

rollers

82, 84 which in turn are driven by motor 86 through a primary drive belt 88 which is driven by pinion 90 and gear 92 which are concentrically mounted. A secondary timing belt 94 having internal gearing projections 96 thereon is wound around gears 93, I which are attached respectively to

rollers

82, 84. Heated platen 22 is placed between

rollers

82 and 84 and below idler roller W2 and belt 80 is wound around

rollers

82, 84, 102 and passes over the upper surface of platen 22. The paper to be heated is inserted between the belt 80 and platen 22.

The

rollers

82, 84 are supported for rotation on

eccentric shafts

104, 106 respectively so that as they are driven for rotation by drive belt 94, they are caused to wobble and assume

position

82A and 84A shown by dotted lines, during the rotation. This causes the belt 80 to rub against and move relative to the paper as the paper is being moved across platen 22 and thereby averages out the contact of any high spots on the belt with the paper. Without this rubbing or agitation of the belt over the paper as it is driving the paper, high spots may cause the paper to become unevenly heated and hence to have the pattern of the belt printed" on the paper. With the agitation of the belt 80, this unevenness is overcome.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

What is claimed is:

1. Apparatus for quickly and uniformly heating an exposed heat developing type paper comprising:

a curved platen comprised of a single layer of resistive material, adapted to engage on the convex side thereof the heat developing paper,

moving means held snugly against the convex surface of said platen layer, and movable relative to said layer,

means for driving said moving means relative to said layer,

guide means for receiving the paper and guiding the paper between said moving means and said platen layer to cause the paper to move over said platen layer as said moving means is driven over said platen layer,

electrical power means connected to said platen layer for causing current to flow through said layer of resistive material and correspondingly heat said layer,

means to sense the temperature of said platen layer and correspondingly control the power of said platen layer to maintain said platen layer at a predetermined temperature, means for causing said moving means to be agitated relative said paper, as said moving means is moving said paper over said platen layer thereby minimizing the moving means surface configuration from being imprinted on said paper.

2. Apparatus of claim 1 with said electrical power means comprising a transformer having a primary winding of many turns and having a secondary winding of less than six turns,

said platen layer being in said secondary winding of less than six turns.

3. The apparatus of claim 1 with said electrical power source comprising a transformer core,

a primary winding of many turns being on said transformer core and being connected to said power source,

said platen means being in the secondary winding of said transformer core and having substantially fewer windings than said primary winding.

4. Apparatus of claim 1 with said platen means having notches cut along its periphery to form a plurality of spaced legs along the periphery and to concentrate current flow in the legs thereby raising the temperature in the legs to insure more uniform temperature of the platen means.

5. The apparatus of claim 1 with said means for moving the heat responsive member comprising belt means which is driven over said platen surface,

roller means around which said belt means is placed being positioned to hold said belt means in intimate contact with said platen surface,

said roller means being mounted for eccentric rotation to cause said belt means to have a reciprocal movement relative said heat-responsive member as said belt means is moving over said platen surface.

6. Apparatus in claim 1 with means for moving the paper over said platen surface as the paper is being developed to provide an average heat to said paper to insure uniform heating of said paper,

said platen surface being polished to facilitate movement of the paper over the surface, improve heat transfer to the paper from the surface and improve heating uniformity of the paper.

7. Apparatus for quickly and uniformly heating an exposed heat developing type paper comprising:

a curved platen comprised of a single layer of resistive material adapted to engage on a convex side thereof the heat developing paper,

means for driving for said moving means relative to said layer,

means to sense the temperature of said platen layer and correspondingly control the power to said platen layer to maintain said platen layer at a predetermined temperature,

a plurality of spaced legs being along a periphery of said platen means with said legs being between said electrical power means and said platen layer so that the current flowing through said platen layer flows through said legs causing a higher current density in said legs thereby raising the temperature in the legs to assure more uniform temperature in the remainder of the platen layer.

i t it 0' k

Claims

1. Apparatus for quickly and uniformly heating an exposed heat developing type paper comprising: a curved platen comprised of a single layer of resistive material, adapted to engage on the convex side thereof the heat developing paper, moving means held snugly against the convex surface of said platen layer, and movable relative to said layer, means for driving said moving means relative to said layer, guide means for receiving the paper and guiding the paper between said moving means and said platen layer to cause the paper to move over said platen layer as said moving means is driven over said platen layer, electrical power means connected to said platen layer for causing current to flow through said layer of resistive material and correspondingly heat said layer, means to sense the temperature of said platen layer and correspondingly control the power of said platen layer to maintain said platen layer at a predetermined temperature, means for causing said moving means to be agitated relative said paper, as said moving means is moving said paper over said platen layer thereby minimizing the moving means surface configuration from being imprinted on said paper.

2. Apparatus of claim 1 with said electrical power means comprising a transformer having a primary winding of many turns and having a secondary winding of less than six turns, said platen layer being in said secondary winding of less than six turns.

3. The apparatus of claim 1 with said electrical power source comprising a transformer core, a primary winding of many turns being on said transformer core and being connected to said power source, said platen means being in the secondary winding of said transformer core and having substantially fewer windings than said primary winding.

5. The apparatus of claim 1 with said means for moving the heat responsive member comprising belt means which is driven over said platen surface, roller means around which said belt means is placed being positioned to hold said belt means in intimate contact with said platen surface, said roller means being mounted for eccentric rotation to cause said belt means to have a reciprocal movement relative said heat-responsive member as said belt means is moving over said platen surface.

6. Apparatus in claim 1 with means for moving the paper over said platen surface as the paper is being developed to provide an average heat to said paper to insure uniform heating of said paper, said platen surface being polished to facilitate movement of the paper over the surface, improve heat transfer to the paper from the surface and improve heating uniformity of the paper.

7. Apparatus for quickly and uniformly heating an exposed heat developing type paper comprising: a curved platen comprised of a single layer oF resistive material adapted to engage on a convex side thereof the heat developing paper, moving means held snugly against the convex surface of said platen layer, and movable relative to said layer, means for driving for said moving means relative to said layer, guide means for receiving the paper and guiding the paper between said moving means and said platen layer to cause the paper to move over said platen layer as said moving means is driven over said platen layer, electrical power means connected to said platen layer for causing current to flow through said layer of resistive material and correspondingly heat said layer, means to sense the temperature of said platen layer and correspondingly control the power to said platen layer to maintain said platen layer at a predetermined temperature, a plurality of spaced legs being along a periphery of said platen means with said legs being between said electrical power means and said platen layer so that the current flowing through said platen layer flows through said legs causing a higher current density in said legs thereby raising the temperature in the legs to assure more uniform temperature in the remainder of the platen layer.