US2585893A - Press for photographic dry mounting - Google Patents

Description

2 SHEETS-SHEET l 'D. K. YOUNG PRESS F OR PHOTOGRAPHIC DRY MOUNTING l] mun lllllll ll oow-uunnnnou Hnoooonnnon.

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INVENTOR Donald K. Your Feb. 12, 1952 YOUNG I 2,585,893

PRESS FOR PHOTOGRAPH 11C DRY MOUNTING Filed Oct. 21, 1949 2 SHEETS*=-SHEET 2 23 I 36 2a 2/ lb 1.9 11 9 I all 1a 10 1 2s 1:"25 as 14 42 1:

- 2 /1 ,,f f 5M8 F AL I 32 if 6 as 400' 3 IN Vf/VTOR Donald .K. Your! 5 f 6% Patented Feb. 12, 1952 PRESS FOR PHOTOGRAPHIC DRY MOUNTING Donald K. Young, Rugby, England Application October 21, 1949, Serial No. 122,726 In Great Britain October 26, 1948 12 Claims. 1

The present invention relates to presses for use in photographic dry mounting and for like purposes, that is to say purposes in which a combination of heat and pressure has to be applied to relatively thin material over a relatively large area.

The most satisfactory known press for photographic dry mounting comprises a base having a flat upper surface on which can be laid the mount and photographic print, having the dry mounting tissue between them. Hinged at one extremity of the base is a top plate which is heated by resistive elements, thermostatically controlled, and which is arranged to exert pressure through the operation of a pivoted handle and a system of levers attached to the top plate. The top plate is in some cases counterbalanced by means of a weight attached to a cable which passes over a pulley. v

This known press suflfers from a number of disadvantages. One of these is that the maximum size of mount which can be accommodated during a single pressure application (irrespective of the size of the print and tissue) is limited by the size of the top plate because of the hinge at the back and the pivoted handle at the front. Secondly, since the pressure is applied to the centre of the top plant, it is necessary that this plate should be stifi. In practice this means that it must be relatively massive, and consequently have a relatively high thermal capacity. The time taken for the top plate to reach working temperature is therefore usually considerable. Thirdly, when counterbalancing is employed, the system used requires that the press be fitted with legs in order to allow the counterbalancing weight to fall when the top plate is raised. Fourthly, a relatively large number of working parts is exposed, and therefore liable to collect dust which cannot be readily removed, and may furthermore be considered unsightly. There is the further disadvantage that pressure has to be applied manually.

The present invention has for its principal object to provide a press, suitable for use in photographic dry mounting, in which some or all of the above-mentioned disadvantages are overcome or at least substantially reduced.

According to the present invention, a press for photographic dry mounting and like purposes comprises a base plate, a top plate, means for heating one of these plates, and electro-magnetic means for generating a magnetic field between the two plates to exert attractive force between them over a substantial part of their opposing surfaces. Since pressure can be applied over a relatively large area, the top plate can be made of much lighter construction than with known presses and its thermal capacity can be correspondingly lower. Electric heating means can conveniently be arranged within the top plate which may be made hollow. The top plate is preferably mounted so as to be capable of being swung about a horizontal axis away from and towards the base plate, the axis being preferably spaced, in a horizontal direction, at a considerable distance from the nearer edge of the top plate. Thus the axis may be defined by hinges or pivots carried upon arms or brackets extending from the base plate. The weight of the top plate is preferably counterbalanced, for example by means of one or more springs. For reasons of safety, as will be explained more fully later, it is preferable that the weight of the top plate should be more than counterbalanced so that, in the absence of magnetic attraction, it tends to swing away from the base plate. Other features of the invention will be apparent from the following description of one embodiment, which is given by way'of example, with reference to the accompanying drawings, in which Figure 1 is an underside plan view of the embodiment, with cover removed,

Figure 2 is a plan view of the embodiment with a small part sectioned,

Figure 3 is a view in section along-the line 33 of Figure 1,

Figure 4 is a view in section on the line 4-4 of Figure 1,

Figure 5 is a circuit diagram of the embodiment, and t Figure 6 is an enlarged view of a portion of Figure 3.

Referring to the drawings, the baseportion comprises a frame If! having a detachable cover plate ll (Figure 3) and supporting an electromagnet [2. The electromagnet is inthe form of two iron castings, namely a cup-shaped casting I3 and a central casting ML. The gap between the poles is a square annulus and is filled with non-magnetic material [5 so that the upper surface of the electromagnet is flat and continuous. The working surface of the base plate is provided by a thin sheet [6 (Figure 4) of chromium plated brass having its edges upset over the edges of the part l3.

The top plate is constituted by a steel platten l1 overlaid by a chromium plated brass sheet I8 having its edges upset over the edges of the platten 11. 'On'the upper surface of theplatten I! are fixed heater elements each comprising an insulating support |9 wound with resistance wire l9 (Figure A cover is fixed to the platten l1 and encloses the heater elements.

Two arms 2| and 22 joined at one end by a rod 23 are rotatably mounted at their opposite end on pivot pins 24 fixed to the base portion. Each arm has near its pivoted end a short cranked portion 25 to which is attached one end of a spring 26, the other end of which is fixed to a lug 21 on the base portion. Intermediate their ends the arms 2| and 22 are attached pivotally to the cover 20. As shown in section in Figure 2 a bolt 28 passes through the cover 20, a fibre washer 29 and the arm 2| into a lever bolt 30. The freedom of the joints permitting rocking movement of the top plate can thus be adjusted by means of the two bolts 30. By raising and lowering the rod 23 the top plate can be raised and lowered. The springs 26 are arranged to maintain the top plate normally in its raised position withuone edge of each of the lever portions 25 in engagement with a stop 3| which may be of rubber (see Figure 3).

A thermostat (Figure 3) is provided to control the heating of the platten I! and can be adjusted-by means ofv a knob 36. A thermometer 3'! may also be providedto'give visual indication of the temperature. A push-button switch 33 is provided on the base portion as shown in Figure 2 to control the supply of current to the excitins coil 33 of the electromagnet.

Asv seen in Figure 1, the base portion I0 is arranged to accommodate rectifiers 32 by which rectified current'can be supplied to the exciting coil 33 of the electromagnet. The circuit dia-- gram of the arrangement is shown in Figure 5 in which components are given the same references as in' the other figures. Alternating current is applied at terminals 34 and its supply to the press is controlled by a main switch 39. When this switch is closed current is supplied by leads to the heater windings l9 through the switch 40 of the thermostat 35 already described. Current also flows through the rectifiers 32 to the exciting winding 33 of the electromagnet, this current being controlled by a safety switch 4| and the push-button switch 38. As shown in Flguresl and 4, the safety switch 4| is a microswitch arranged to be operated by a lever 42 pivoted centrally to the electromagnet at 43 and having the end opposite to that engaging the switch 4| in engagement with one end of a feeler rod 44 slidable in an aperture in the electromagnet. The left end of the lever 42 is pressed downward, and consequently the rod 44 is urged upwards by a spring 45. When pressure is applied to the sheet l6 covering the base plate, the rod 44 is depressed and the switch 4l is closed. An indicator lamp 4! is connected to indicate when the main switch 39 is closed. This lamp is also shown in Figure 2. v

In operation the top plate is held automatically by the two arms 2| and 22 well clear of the base plate, thus giving good access to the opposed surfaces of the top plate and base plate, both for cleaning purposes and also for the proper arrangement of the mount and print (shown at 48 in Figure 3) upon the surface of the base plate.

When the mount and print with the interposed mounting tissue have been correctly disposed upon the surface of the base plate, the handle 23 is lowered thus bringing the top plate into contact with the material to be pressed. The heating means within the top plate will have been previously switched on by closure of the switch 39, and, owing to the low thermal capacity of the top plate, the heating up of the top plate is eiiected quickly. When the handle 23 has been lowered sufiiciently for pressure to have been exerted on the rod 44 to close the micro-switch 4|, the push-button switch 38 is operated to energise the winding 33 and. thus generate a magnetic field in the gap of the electromagnet. The top plate acts as the armature of the magnetic cir cuit, tending to offer a path of low reluctance to the flux between the two poles of the electromagnet and in this way magnetic pressure is exerted between the two plates over a large part of their surface.

Owing to the relative uniformity of the force applied magnetically between the two plates, the base plate can also be of less massive construction than with known presses and the total weight of the press can be correspondingly reduced. If it be desired to heat the base plate instead of, 'or in addition to, the top plate, such heating will takeplace more quickly owing to the lower heat capacity.

One feature of the embodiment described which renders it safe in operation is the counterbalancing of the weight of the top plate in such a way that this plate tends to rise. The risk of the plate swinging down upon the fingers of anyone manipulating a print upon the base plate is thus avoided. A further safety device is the micro-switch 4! which prevents the operation of the electromagnet until the top plate is in engagement with the material to be pressed so that the possibility of the fingers being pinched is avoided.

It will be noted that owing to the location of the pivot axis for the top plate a mount of much larger size than the top plate can be accommodated.

Instead of using a thermostat, the heating of the top plate may be controlled by means of a time-control device, which may be of known type, whereby the heating circuit is closed for recurrent periods, the duration of such periods being variable.

A thermostatically-controlled auxiliary heater may be provided upon the base to act as a heat source for a tacking iron which is used for tacking the print and mount together at suitable points when arranging them on the base plate before lowering the top plate. Two such tacking irons are conveniently provided, one being in use whilst the other is heating up.

I claim:

1. A press for photographic dry mounting comprising a base plate, a top plate, means to heat at least one of said plates, and. an electromagnet having its pole surfaces adjacent one of said plates and on the side thereof remote from the other of said plates, said pole surfaces lying in a plane parallel with said one plate and having an annular gap between them, and said other plate being of magnetic material and substantially co-extensive with said surfaces to exert attractive force between said plates.

2. A press for photographic dry mounting comprising a base plate, a top plate mounted for pivotal movement relatively to said base plate about an axis at a substantial distance from the nearer edge of said top plate, means to heat at least one of said plates, and electromagnetic means to generate a magnetic field between said plates to exert attractive force between said plates, one of said plates being of magnetic material and constituting an armature, and said electromagnetic means being constituted by an electromagnet having its pole surfaces lying in a plane parallel with the other plate, and having an annular gap between them.

3. A press for photographic dry mounting comprising a base plate, a top plate mounted for pivotal movement relatively to said base plate about an axis at a substantial distance from the nearer edge of said top plate, spring means to counterbalance the weight of said top plate to maintain said top plate normally spaced from said base plate, means to heat at least one of said plates, and electromagnetic means to generate a magnetic field between said plates to exert attractive force between said plates, said electromagnetic means being constituted by an electromagnet having its two polar surfaces fiat and coplanar.

4. A press for photographic dry mounting comprising a base plate, a top plate, two arms mounted near one end for pivotal movement about an axis fixed relatively to said base plate, means for pivotally supporting said top plate between said arms intermediate the ends thereof, means to heat at least one of said plates, and electromagnetic means to generate a magnetic field between said plates to exert attractive force between said plates.

5. A press for photographic dry mounting comprising a base plate, a top plate, means to heat at least one of said plates, electromagnetic means including an exciting winding to generate a magnetic field between said plates to exert attractive force between said plates, switch means to permit energising of said exciting winding when actuated, and means operating automatically upon lowering said top plate close enough to said base plate to prevent insertion of a finger for actuating said switch means.

6. A press according to claim 5 including a further, manually-operable switch in series with said switch means.

7. A press for photographic dry mounting comprising a base plate having a substantially fiat and continuous upper surface, a top plate having a substantially fiat and continuous under surface, means for pivotally supporting said top plate for movement of said surfaces into and out of contact with one another, means to heat one 10. A press according to claim 9, wherein the 7 gap between said polar surfaces is filled with non-magnetic material having a surface coplanar with said polar surfaces.

11. In a press, the combination of upper and lower plates, means mounting one of said plates for movement into and out of contact with the other plate, a thin sheet covering the inner face of one of said plates and being secured to said plate at its periphery, a feeler member engaging said sheet near the center thereof and normally urging the center portion of said sheet out of contact with its supporting plate, a normally open switch positioned to be operated to closed position by said feeler when the central portion of said sheet is moved into contact with its supporting plate, electrical means for exerting clamping pressure on said plates, and a circuit controlled by said switch for energizing said electrical means.

12. A press according to claim 11 wherein said thin sheet is formed of non-magnetic material, and said electrical means comprises an electromagnet embodied. in one of said plates and establishing a magnetic field exerting an attractive force on a magnetic part embodied in the other plate.

DONALD K. YOUNG.

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

UNITED STATES PATENTS Number Name Date 1,777,642 Harrington Oct. 7, 1930 2,305,010 Kenney et a1. Dec. 15, 1942 2,369,362 Marziani Feb. 13, 1945 FOREIGN PATENTS Number Country Date 571,598 Great Britain Aug. 31, 1945

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