US2934395A

US2934395A - Thermal-type marker

Info

Publication number: US2934395A
Application number: US670810A
Authority: US
Inventors: Basiago Raymond
Original assignee: McGraw Edison Co
Current assignee: McGraw Edison Co
Priority date: 1957-07-09
Filing date: 1957-07-09
Publication date: 1960-04-26
Anticipated expiration: 1977-04-26

Description

April 1950 R; BASIAGO 2,934,395

THERMAL-TYPE MARKER Fild July 9, 1957 i207" 2?Z"\'i?d INVENTOR i? Rg n Banjo United States Patent C THERMAL-TYPE MARKER Raymond Basiago, Morris Plains, N.J., assignor to McGraw-Edison Company, Elgin, 111., a corporation of Delaware Application July 9, 1957, Serial No. 670,810

Claims. (Cl. 346139) This invention relates to thermal devices for marking heat-sensitive paper or other such material, and more particularly it relates to improved forms of thermal markers adapted for use as indexing devices in dictating machnies.

It is a common practice to provide dictating machines with an indexing head that is moved in correspondence with the traveling movement of the carriage for making marks on an index slip at points therealong corresponding to places on the record where the dictator wishes to make length, correction, rush or other indications in connection with the dictated matter. Such marks usually been made by punching the index slip or by scratching a slip made of specially-treated paper to expose an underlying film or lamination of a different color. The present marker is of the thermal type having an exposed conductor element which can be electrically heated to make fine marks on specially-treated heat-sensitive paper,

An object of my invention is to provide a simplified design of thermal marker which has long life and low power requirements, and which is economical to produce. In particular, an object of my invention in this respect is to provide a design which eliminates the expense of fine resistance wire and of complicated procedures in suitably mounting such wire.

In order to obtain the necessary heating within reasonable power limits a thin thread-like conductor element as of Nichrome is commonly used. If a fine resistance wire of such material is employed, difficult production problems are encountered in providing the wire with a firm protective backing or support while still exposing an edge of the wire for contact with the heat-sensitive paper, in concentrating the heating effect to the exposed portion of the wire, and in making suitable lead wire connections to such fine wire. These problems are accentuated further when the thermal marker is to have several exposed heater elements which are to be selectively energized for making marks in different rows or columns for indicating different indexing functions such aslength, correction, rush, etc.

By the present invention these problems are solved economically by a simple design which uses a thin, metal foil as the conductor element. This foil is formed as by "stamping so as to have a narrow heater stripprovided with integral low-resistance side extensions forming width of the heater strip is reduced sufiiciently to pro- "ice vide it with the desired high resistance. Also, by such grinding the exposed surfaces of the several heater elements are made flush with a planar surface of the mounting structure for even engagement with a flat surface of a material to be marked. Such device comprises only low-cost parts which can be fabricated economically to close tolerances into a solid unitary structure of an efiicient design capable of long periods of use without mechanical or electrical failure.

These and other objects and features of my invention will be apparent from the following description and the appended claims.

In the description of my invention reference is had to the accompanying drawings, of which:

Figure 1 is a side view of a marking device of my invention and of a carriage therefor, showing the marking device in operative engagement with an index slip of a dictating machine, the mounting for the index slip and for the carriage being shown in cross section;

Figure 2 is a plan view of the apparatus in Figure 1;

Figure 3 is a side elevation of a first subassembly used in producing the marking device of my invention;

Figure 4 is a plan view showing a subassembly of the device in a second stage of completion;

Figure 5 is a side elevational view of the subassembly of Figure 4;

Figure 6 is a fractional cross sectional view to enlarged scale showing the marking device as it appears on the line 66 of Figure 7;

Figure 7 is a cross sectional view taken on the line 7-7 of Figure 6;

Figure 8 is an elevational end View of a marking device; and

Figure 9 is a schematic diagram of a control circuit for the present marking device.

The present marking device 10 is provided preferably in a block shape having a planar bottom face 11 provided with one or more heater elements 12 (three being shown by Way of example and referred to respectively as 12a, 12b and Me) which are flush with the bottom face and disposed in a central plane lengthwise of the device. The housing 13 is preferably made of a suitable plastic such as Lucite having holes 14 in its opposite side walls (Figure 8) for receiving trunnions 15 of a U- shaped mounting spring 16. The back end portion of this spring is mounted flat on the top side of a carriage 17 and secured thereto by a clamping screw 18. The carriage is, for example, in the form of a plate having apertured lugs 19 turned down at its sides through which is fitted a sleeve bearing 20. The bearing is mounted slidably on a support rod 21 fractionally shown. A rear portion of the carriage rests on a second cross rod 22 parallel with the first rod 21, and is retained slidably thereon by two lugs 23 struck downwardly from the side portions of the carriage at a sufiicient distance for engagement with the underside of the rod 22. Under influence of the mounting spring 16 the marking unit is pressed downwardly fiat against an index slip 24 of a heat-sensitive paper supported in a holder 25 having the opposite edges 25a folded over to overlap the opposite edges of the slip and retain the slip in place. The slip has three tracks lengthwise thereof referred to respectively as 26a, 26b and 260, which are adapted for receiving marks from the

respective heater elements

12a, 12b and to indicate respectively length, correction and rush. Such marks are short colored lines as indicated, for example, at 27a, 27b and 270 in Figure 2. The heat-sensitive paper may be of any commercial form such, for example, as that supplied by the Minnestoa Mining 8; Manufacturing Company of St. Paul, Minnesota. This is a white paper which turns to a dark color at any point where it is suitably heated.

The heater elements 12 are formed from a rectangular piece 28 of metal foil having initially an excess height as shown in Figure 3. This foil is made preferably of Nichrome and has about .002 thickness. The foil is cut out as by stamping and in the same opera,- tion is provided with three triangular holes 29a, 29b and 29c along the bottom edge thereof. The portions of the foil below these triangular openings form the

heater strips

12a, 12b and 12c aforementioned. Placed fiat against the opposite sides of the lower apertured portion of the foil to a height of nearly the apices of the triangular holes 29 are side plates 30 of insulating material such as of Micarta. These plates may be typically about .015" in thickness. The inside surfaces of these insulator plates are secured to the foil and to each other through the holes 29 by means of a suitable thermoplastic cement such as Ciba Araldite No. 502. This cementing is done by coating the adjoining surfaces, clamping the plates together against the foil, heating the assembly to about 100 C. for ten to thirty minutes, and then allowing the same to cool to room temperature. After the laminated structure is so formed the upper excess portion of the foil 28 is cut off at the line 31 in Figure 3 through the apices of the triangular holes 29a, 29b and 290 so as to form

successive terminals

32a, 32b, 32c and 32d extending from a side of the laminated foil plate structure. The upper tabs of these terminals which extend above the side plates 30 are then folded over against the top end face of one of these plates and

respective lead wires

33a, 33b, 33c and 33d are soldered thereto as indicated in Figure 4. These lead wires have a suitable insulative covering such as of Formvar, and are bunched together and lead from the subassembly unit 28-36 along the top edge thereof. Next, the bottom face of the subassembly unit is ground down until the width of the heater strip elements 12 is reduced to the desired dimension to cause the heater elements between the successive terminals 32 to have the desired high resistance. As a final operation, this subassembly unit is mounted in the housing 13 with the bottom face thereof projecting slightly below the housing and with the lead wires 33 running out one end thereof. Such housing may be, for example, a block of suitable plastic molded with a central slot 34 running out one end thereof to receive the subassembly unit, and the unit may be secured in place by cementing as with Duco cement. Preferably, the block 13 is made of clear plastic and the cement for holding the unit in place is colored black as by India ink, so that the finished unit has the appearance of a clear plastic block with a fine coloredline running lengthwise thereof to indicate the place of the heater elements. As before described, the housing has side holes 14 receiving the end trunnions of the mounting spring 16.

A control circuit for the marker is illustrated in Figure 9. This circuit is connected through a transformer 35 to a source of power designated by the terminals 36. In the control circuit there is a rectifier 37, load resistor 33 and condenser 39. The power for heating the thermal marker elements 12 is derived by discharging the condenser 39 through the circuit 40. The circuit 46 is connectable selectively across the

respective heater elements

12a, 12b and 120 via respective pushbutton switches indicated at 41a, 41b and 410. For example, when one of these switches is depressed the circuit is closed across the condenser 39 through the respective heater element to cause the condenser to be discharged through that element. This causes the heater element to be heated momentarily sufiiciently to make a suitable mark on the associated heat-sensitive index slip 24, the time of the heating being established by the time constant of the condenser 39 and resistance in the discharge circuit. It is found that about .27 watt second of power is ample for momentarily heating the respective heater elements and that such amount of heating power is obtained when the condenser 39 has about 390 mf. and is charged to about 30 volts. Although the operator may continue to hold one or another of the control switches 43 closed for a substantial length of time, it is only the initial discharge from the condenser 39 that is effective in heating the selected marker element because the load resistor 33 is sufliciently high to prevent a continued heating of that element to an operative temperature. However, the load resistor 38 will allow the condenser to be quickly recharged for a successive marking operation as soon as the control switch is released.

The particular embodiment of my invention herein shown and described is intended to be illustrative and not limitative of my invention since the same is subject to changes and modifications without departure from the scope of my invention, which I endeavor to express according to the following claims.

I claim:

1. A thermal-type marker for operation on a heatsensitive material comprising an elongated laminated structure including two insulating plates and an intervening metal foil, said foil comp-rising a narrow, elongated heater strip extending lengthwise of said laminated structure and provided with a plurality of integral side extensions at right angles to the lengthwise dimensions of said heater strip forming electrical terminals extending beyond one side of said laminated structure, said terminals having dimensions in the direction along said strip substantially greater than the width of said strip, said laminated structure having a side face with an exposed edge of said strip portion of the foil flush therewith for contact with said heat-sensitive material, and lead wires connected to said terminals for conducting current to said strip portion to heat the same.

2. A selectively-energizable thermal-type indexing marker for marking on a heat sensitive material in respective tracks thereon, comprising an elongated laminated structure of two insulating plates and an intervening metal foil, said foil comprising a narrow elongated heater strip lengthwise of said laminated structure and provided with integral side extensions at right angles to the lengthwise dimension of said heater strip and at intervals therealong forming electrical terminals, said terminals extending beyond one side of said laminated structure and having a width dimension along said heater strip substantially greater than the width of said strip, said laminated structure having a side face exposing an edge of said strip of said foil for contact with said heatsensitive material, and lead wires connected to said terminals for conducting current to said respective strip port10ns of the foil.

3. The thermal-type marker set forth in claim 1 wherein said terminals have an increasing width proceeding from said heater strip.

4. A thermal-type indexing marker adapted for selectively marking in rows on a heat-sensitive paper, comprising a body of insulating material having a side face for engaging said paper and having a one piecemetal foil embedded in said body at right angles to said side face with an edge of the foil substantially flush with said side face, said foil comprising a single narrow heater strip at said side face having integral side extensions at right angles to the lengthwise dimension of said heater strip and at intervals therealong forming electrical terminals, said terminals having width dimensions along the heater strip greater than the width of the strip itself leading out of another face of said body, and lead wires connected to said terminals respectively for conducting current to heat selectively the heater strip portions of said foil between successive terminals.

5. The indexing marker set forth in claim 4 wherein said terminals have a width dimension along said heater strip which increases proceeding from said heater strip and the average width of each of said terminals is substantially greater than the width of said heater strip whereby to confine largely the heating efiect of an electrical current to the heater strip.

References Cited in the file of this patent UNITED STATES PATENTS Glynn Sept. 26, Cox June 17, Holden et al. May 18, Greig July 6, Boyan Ian. 8,

FOREIGN PATENTS Great Britain May 11,