US2557182A - Printer with contrast filters - Google Patents

Description

June 19, 1951 v. J. FORGETT 2,557,182

PRINTER WITH CONTRAST FILTERS Filed Dec. 9, 1947 4 Sheets-Sheet 1 INVENTOR. yfi wwm x ss\ BY N A TTOZA/EXY.

June 19, 1951 .v. J. FORGETT 2,557,182 PRINTER WITH CONTRAST FILTERS Filed Dec. 9, 1947 4 Sheets-Sheet 2 MN M mmmwq.

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PRINTER WITH CONTRAST FILTERS Fiied Dec. 9, 1947 4 Sheets-Sheet 4 Patented June 19, 1951 UNITED STATES PATENT OFFICE PRINTER WITH CONTRAST FILTERS Valmore J. Forgett, Ridgefield, N. J. Application December 9, 1947, Serial No. 790,667

1 Claim. 1

This invention relates to apparatus for printing successive negatives on a strip of photographic paper and for compensating for differences in the contrast of the negatives so that good prints can be obtained from all of the negatives without using paper of diiferent emulsion coating for negatives of different contrast.

It has been possible to obtain prints of normal contrast from negatives that are flat or too contrasty by making the prints on paper that has special emulsion coating, different emulsions being used for the flat negatives and for those that are too contrasty. With commercial printers that employ strips of photographic paper, it is not practical to print individual negatives of a particular batch on different kinds of paper because unless the negatives of each batch are printed successively on the same strip, the subsequent sorting of the prints after development becomes an intolerable expense for the printing establishment.

One solution that has been proposed is the use of a photographic paper that is coated with an emulsion which gives diiferent degrees of contrast depending upon the quality of the light used to make the exposure. For example, with a negative of normal contrast, the print can be made flat or excessively contrasty by'using light of different color when exposing the print. With such paper it is possible, therefore, to compensate for undesirable contrast qualities of a negative by merely changing the color of the light in the printer.

It is an object of this invention to provide a photographic printer with improved means for compensating for variations in the contrast of negatives, and features of the invention relate not only to the apparatus by which the quality of the light is changed, but also to control means for the light changing apparatus. One embodiment of the invention includes adjustment of the timing of the printer for negatives of different density, and automatic change in the light quality with the adjustment of the timing.

In other modifications of the invention the control of the timing for different density of the successive negatives, and the control of the quality of the light are separate. Some features of the invention can be used with or without auto matic timing mechanism, but the preferred embodiment of the invention includes light-responsive timing mechanism. The change in the quality of the light is generally a change of color, and it is preferably effected by the use of filters placed in the path of the light that is used to make the exposure, but the differences in color can be eifected by using different lamps.

Another object of the invention is to provide an improved photographic printer with means for changing the quality of the light to compensate for differences in the contrast of the successive negatives, and to provide automatic control means for returning the printer to its normal condition after each change in the quality of the light to accommodate an oif-standard negative.

Other objects, features and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views,

Fig. l is a front view, partly broken away and in section, of a printer embodying this invention,

Figs. 2 and 3 are sectional views taken on the lines 2-2 and 3-3, respectively, of Fig. 1.

Fig. 4 is an enlarged sectional view taken on the line 4-4 of Fig. 3.

Figs. 5-7 are wiring diagrams, each showing a diflerent modification of the invention.

The printer includes a frame H supported on a table [2 that has legs H3. The printer illustrated is one in which the negative is supported at a station spaced from the photographic paper on which the print is to be made, and an image of the negative is focused on the paper by an intervening lens. The negative station comprises a transparent or translucent support l5 that covers an opening in the table 12. The paper 16 passes over a holder ll near the top of the frame H. A lens it is supported within a housing !9 of the printer above the negative station and in position to throw an image of the negative on the paper it. in the machine illustrated, the image of the negative is the same size as the negative, but in some machines the pictures are onlarged at the time that they are printed.

The print is made with light from a lamp housing 28 located under the top of the table I 2. During the time that illumination from the lamp housing is passing through the negative to the paper to make a print, the negative station is covered by a hood 22 that swings down into posi-- tion to prevent light from escaping into the room. The hood 22 is attached at its upper end to the housing l9 by hinges 24.

The paper [8 is originally wrapped in a reel 26 on a drum 2'! that is supported from the frame H by spindles 28. The paper passes from the reel 26 across a guide roll 39 and then across the 3 paper holder ll that supports the paper at the correct location for exposure. The holder l'l can be open below the paper, but preferably includes a glass panel 32 against which the paper is gently pressed so that the paper will always present a flat surface for receiving the projected image of the negative that is to be printed. The margin portions of the paper that are not to be exposed rest on a mask, in a manner well understood in the art.

Beyond the paper holder H, the paper travels across another roller 34 and then turns down ward and passes between feed rolls 3 and 3E. The feed roll 35 is power driven with an intermittent operation that turns the roll 35 after each exposure and for a peripheral distance exactly equal to the desired length of a print, including the side borders of the print. The other feed roll 35 is an idler roll, but serves to maintain the paper in firm contact with the power driven roll 35 to prevent the paper from slipping on the surface of the roll 35.

The paper strip it passes around a substantial part of the circumference of the idler roll35 to change the direction of the run of the paper. From the idler roll 36, the paper it travels upward and winds around a drum 38 which is sup" ported from the upper part of the frame H by spindles 39. The drum 38 rotates as a unit with the forward spindle 39, and this forward spindle is driven from the feed roll 35 by a spring belt 4| and pulleys 52 and d2 connected with the feed roll 35 and forward spindle 3-9, respectively. The ratio of the diameters of the pulleys i2 and 42 are chosen so as to give the drum 38 the necessary speed to Wrap the paper 6 at the rate that the paper comes from the feed rolls, and even before there is any other paper yet wrapped on the drum 33. This means that the speed of the drum 33 would be excessive as soon as some convolutions of paper were on the drum 38 and the diameter of the drum was thus, in eifect, increased. In order to compensate for the increase in diameter of the reel of paper as it wraps around the drum 38, the spring belt M is given a comparatively light tension, and the pulley faces are shaped to permit the belt ll to slip as much as necessary to maintain the correct speed of rotation of the drum 3B. This combination maintains the paper strip under a certain amount of tension during the operation of the machine.

The particular mechanism used for causing intermittent operation of the feed roll 33 is not important. For purposes of this invention it is sufficient to understand that the power-driven feed roll 35 is driven through a chain and sprocket connection 43 (Fig.3) from a shaft Ml that is turned periodically by a one-turn clutch t5, the driving side of which is rotated continuously by an electric motor 46 through reduction gearing El. The clutch 455 is engaged by a control element attached to a rod 49. This rod i!) extends downward to a foot pedal 5! (Fig. l) and it has an actuator 52 which extends into the lamp housing 29 to pull the hood 22 down and to operate a momentary contact electric switch 54 that lights the lamp in the housing 26 and starts the operation of a timer mechanism 56 (Fig. 2) which controls the duration of the exposure period.

Fig. 2 shows the path of the light from a lamp 58 in the lamp housing 2! to the paper it on the paper holder ll. Rays from the lamp 58 are concentrated by a condenser til on a refiector Si which directs the rays upward through a negative 52 on the support l5. After passing through the negative, the light travels through the lens l to a partly-transmitting, partly-reflecting element 63. The light that through the refiector element 53 strikes the paper l6 on the paper holder ii and produces the exposure that makes the print. The light that is reflected by the reflector element 63 strikes a light-responsive cell as of the automatic timer mechanism 56.

There are three filter holders 65, 55 and 8'? supported from a post so and movable inde pendently of one another through limited angles of swing about the axis of the post 68. The post 63 is so situated that each of the filter holders $5, 55 and Eli can swing into the path of the light rays that are passing from the lens is to the paper IS on the paper holder 57, or can swing out of the path of the light, as desired. A fixed filter holder 89 is secured within the housing It, and a normal contrast filter is is supported by the filter holder 6d and permanently positioned in the path of the light passing to the paper IS.

Fig. 4 shows the structure of the filter holders E5, 66 and 6? on an enlarged scale. Each of these holders has a hub that turns on the post 68 as a bearing, and each of the filter holders includes a frame in which transparent filter is secured. A filter H rests on a shoulder '12 of the filter holder 65 and is held in place by a snap ring is. A filter li of different color from the filter ll rests on a shoulder 12' of the filter holder 66 and is held in place by a snap ring 53. Another filter of a different color from the filters TI and it is similarly fastened in the filter holder 57, but this third filter is not visible in Fig. 4 because the filter holder 67 is shown in elevation.

Reach rods 853, Si and 82 are connected with the filter holders 65, 66 and 61, respectively, by pins 85 that form pivot connections between the filter holders and the reach rods. The reach rod 89 extends through a slot 86 (Fig. l) in the hous ing l9 and connects with a plunger 88 of a solenoid 89. A cotter pin 94 that connects the reach rod 80 with the plunger 88 provides a pivot connection between the reach rod and the plunger so that the plunger can have oblique motion even through the plunger has only straight-line motion as it slides in the solenoid 83 as a bearing and guide.

A tension spring 93, connected at one end with the cotter pin 9i and at its other end with the housing l9, gives the plunger 88 a bias toward the extended position shown in Fig. 1. With the plunger in this position, the reach rod 89 and filter holder 65 are in a position to locate the filter of filter holder 65 out of the path of the light rays passing from the negative to the paper.

The reach rod BI is similarly connected with a plunger 95 of a solenoid 95, and is biased with a spring 9'! toward the extended-plunger position that locates the filter of filter holder 56 out of the path of the light. In like manner the reach rod 82 is connected with a plunger 98 of a solenoid 99. A spring Ill!) biases the plunger 98 toward the position that locates the filter of filter holder 6? out of the path of the light. Fig. 1 shows the solenoid 99 energized and the plunger 98 drawn in so that the reach rod 82 is pulled toward the right and the filter holder 6'! is in a position to interpose its filter in the path of the light passing to the paper It. The stroke of each of the solenoid plungers and of the reach rods and filter holders that are connected with each plunger is limited at one end by having the plunger strike against the end of the solenoid in which it slides, and is limited at the other end by having the filter holder strike against a wall I03 Il ig 3) which provides an abutment, for determining the position of the filter l 1 old ers.when they are out of the path of the light.

The timer mechanism 56 may be of various conventional constructions and is preferably an electronic timer. In the preferred embodiment of the invention, the timer mechanism is lightresponsive and it may be similar to that disclosed in United States Patent 1,973,468, issued to A. G. Denis on Sept. 11, 1934. Such a timer has a capacitor that is charged at the time that the exposure period begins, and the capacitor discharges through a light-responsive cell the conductance of which depends upon the amout of light that falls upon the light responsive cell. The timer includes an electronic tube that passes current when the charge of the capacitor is below a critical value.

For purposes of this invention it is sufficient to understand that the timer mechanism 56 is connected with a power line I05 (Fig. 5), and that the timer normally supplies current to the coil of a relay i08 which holds an armature I09 against the bias of a spring H0 and away from contacts III and H2. When the momentary contact switch 54 is closed to charge the capacitor of the timer mechanism 56, the flow of current through the coil of relay IE0 is stopped, and the spring IIIJ pulls the armature I09 up against the contacts I I I and I I2.

When the armature I09 touches the contact II2 a circuit is closed through the lamp 58 and the lamp 58 remains lit until the charge in the timer 56 has dropped to a critical value which permits the coil of relay I08 to be again energized so that it will pull the armature I09 away from the contacts III and H2.

The solenoids 89, 95 and 99 are connected with contacts H5, H6 and II! of a 3-position switch I that includes a blade H9. When this blade H9 touches the contact H5, a circuit is closed through the solenoid 89 if the armature 09 of the relay I 08 is in position to touch the contact II2. It will be apparent from this circuit that when the blade H9 is moved to the left to energize the solenoid 89, this solenoid is not energized until the timer mechanism 55 has been operated to close the circuit from the relay contact H2, and the circuit of the solenoid 89 is broken as soon as the timer 56 energizes the relay I03 to extinguish the lamp 58.

The contact H2 is in a common ground line from all of the solenoids 89, 96 and 99, so that when the blade I I9 of the 3-position switch is on the contact I I 6 or i I? to energize the solenoids 96 and 99, respectively, these solenoids are energized only as long as the lamp 58 remains lighted. With a control system such as shown in Fig. 5, therefore, the filters move into and out of the light beam in response to operation of the timer; and when the lamp 53 is extinguished, the filters move out of the light beam and leave the printer in what may be considered its normal condition. The blade II9 of the 3-position switch can be shifted to an oil position in which it will not supply power to any of the solenoids B9, 95 and 99.

Fig. 6 shows the control system for the printer illustrated in Figs. 1 to 3. The timer 55 can be made to give timing periods within different ranges by employing several capacitors in the timer. The actual circuit is not important for purposes of this invention, it being sufficient to understand that the closing of various switches I22, I23, and IM-changes the capacity of the timer and gives longer and shorter period ranges which make the printer capable of operating on very thick and very thin negatives for which the timer would not otherwise be well suited. These switches 122, I23 and I 24 are operatedby buttons bearing the same reference characters, and are located on the front of the housing I9 as shown in Fig. 3. The switches are preferably so constructed that only one switch will remain closed at a time.

The remainder of the wiring diagram shown in Fig. 6 is the same as that shown in Fig. 5, and the solenoids 39, 9G and 99, that hold the filters in the light beam, remain energized during the period that the lamp 58 is lighted, as in the case of the simpler control system shown in Fig. 5.

Fig. 7 shows a modified control system for the filters. In this control system a filter is moved into operative position automatically in response to the operation of the respective switches I22, I23 and I24 that change the timing of the printer.

In order to have the switches I22, I23 and 124 control both the filter-operating solenoids and the capacity of the timer mechanism 59, without conflicting circuits, the capacity of the timer 56 is controlled by relays I28, I 29 and I30 in series with the switches I22, I23 and I24, respectively. If the operator wants a particular filter to move into operation whenever the timer is set for a .dense negative, and other filters to move into position when the printer is set for negatives of other thickness, the control system of Fig. 7 provides apparatus by which these results are ob tained quickly and conveniently. The control system of Fig. 6, however, provides greater flexibility since it permits the use of any selected filter with any selected adjustment of the timer for negatives of different density.

Although the timer has been described with a circuit that closes when a relay is deenergized, it will be understood that modifications can be made to obtain the reverse operation, that is, closing of the circuit upon energizing of a relay. It should be understood further that a control of the light by moving a shutter into position to block the light is the mechanical equivalent of the movement of a switch into position to break a circuit and. extinguish the light.

Other changes and modifications can be made in the construction illustrated and described, and some features of the invention can be used alone or in different combinations without departing from the invention as defined in the claim.

I claim as my invention:

A printer for printing negatives of different contrast of photographic paper having a spe cific emulsion, said printer comprising a negative station, a paper holder spaced from the negative station, illuminating means for passing a beam of light through a negative at said station and to the paper on said holder, a timer for determining the period during which light passes through the negative to the paper, a plurality of filters located between the negative station and the paper holder, supporting means on which the respective filters are independently movable, separate control means for shifting different selected filters into the path of the light beam that travels from the negative to the paper, an automatic timer including a light-responsive element in position to be struck by at least a predetermined part of the light that passes through the negative during the period of exposure of the paper, and including also electric control means that operate the timer to shut off further light to the paper after a given amount of light has struck on the light responsive element, apparatus under the control of the timer for returning the selected filter to its original position out of the path of the light beam, each time that the timer operates to shut 011 the light to the paper, and exposure control means that adjust the timer to operate in response to different amounts of light, said exposure control means being actuated by the separate control means for shifting the filters.

VALMORE J. FORGETT.

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

UNITED STATES PATENTS

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